[270-year cycle Minor Cycle Detailed Analysis: Triple Cycle Edition] Japan Edition  — Chapter 4 (Revised) The 270 Years from 1060 to 1330 AD, Read Through the 83-, 90-, and 55-Year Cycles

【Triple Cycle Detailed Analysis】Japan Edition — Chapter 4 (Revised)

The 270 Years from 1060 to 1330 AD, Read Through the 83-, 90-, and 55-Year Cycles

Subtitle: The Structural Law Confirmed Across Five Consecutive Chapters — “55-year + 83-year overlap within 1 year, 90-year lags by 14 years”

— Starting point revised from AD 1024 to AD 1060 (270-Year Macro-Cycle 4th Transition Point) —

⚠️ This article is an analytical essay based on triple-cycle theory. It does not predict or guarantee the occurrence of specific events. Some correspondences with historical facts include points on which scholarly opinion varies.

About This Revision — Why the Starting Point Was Changed to AD 1060, and Precision Verification

The previous version set Chapter 4’s starting point at AD 1024 (around the end of Michinaga’s era). This revision adopts AD 1060, the 270-year macro-cycle’s 4th transition point.

Precision Verification: Impact of the Starting-Point Change

Previous (origin AD 1024) Revised (origin AD 1060)
Mean error 6.1 years 5.9 years (improved)
55-year within ±5 years 3 times 4 times
Four-chapter pattern 1189–1190 (Yoshitsune’s defeat + Yoritomo’s recognition) 1225–1226 (Jōkyū War)
Pattern meaning “Official establishment of warrior governance” “Warriors reversed judgment on the court for the first time”

The starting-point change slightly improved precision. More importantly, the location where the “four-chapter pattern (55×3 ≈ 83×2)” converges shifted from 1189–1190 to 1221–1226 (around the Jōkyū War).

📌 The Meaning of the “Jōkyū War” as the New Transition Point
Previous transition: 1189–1190 (Yoshitsune’s defeat + Yoritomo appointed Ukonoe no Taishō)
→ “Warrior governance officially approved by the court”
Revised transition: 1221–1226 (Jōkyū War to Goseibai Shikimoku)
→ “Warriors reversed judgment on the court and began governing the nation through warrior law (Goseibai Shikimoku)”
The previous transition was “being recognized by the court.” The revised transition is “surpassing the court.”
The revised transition more vividly captures the essential transformation of this 270-year span.

Introduction — Chapter 4 Confirms the “Five-Chapter Consecutive Pattern”

The moment the 55-year cycle was applied to Chapter 4 (1060–1330), the most important discovery across this entire series was further strengthened.

Calculating the 55-year cycle’s Node 3 from the origin of 1060 yields 1225. The 83-year cycle’s Node 2 falls at 1226 — a 1-year gap.

This is not coincidence. The exact same pattern had been repeating in Chapters 1 through 3.

Five-Chapter Consecutive Pattern Confirmed
Chapter 1 (origin AD 250): 55×3 = 415, 83×2 = 416 (1-year gap) → 90×2 = 430 (14-year lag)
Chapter 2 (origin AD 520): 55×3 = 685, 83×2 = 686 (1-year gap) → 90×2 = 700 (14-year lag)
Chapter 3 (origin AD 790): 55×3 = 955, 83×2 = 956 (1-year gap) → 90×2 = 970 (14-year lag)
Previous Ch. 4 (origin AD 1024): 55×3 = 1189, 83×2 = 1190 (1-year gap) → 90×2 = 1204 (14-year lag)
Revised Ch. 4 (origin AD 1060): 55×3 = 1225, 83×2 = 1226 (1-year gap) → 90×2 = 1240 (14-year lag)
→ Both the “1-year gap” and the “14-year lag” are mathematical necessities (55×3 = 165, 83×2 = 166, 90×2 = 180).
 However, it is NOT a mathematical necessity that these nodes coincide with the Jōkyū War (1221) through the Goseibai Shikimoku (1232) — the era’s greatest historical turning point.

“When civilization and economics transition simultaneously, human society undergoes its greatest upheaval” — this principle has now been confirmed across five consecutive chapters.

Section 0 (New): AD 1060–1086 — From the Macro-Cycle Transition to the Launch of Cloistered Rule

From the 270-year macro-cycle’s 4th transition point (AD 1060), through the zone corresponding to the previous edition’s starting point (around AD 1024), to the launch of cloistered rule (insei) in 1086. These 26 years constitute Chapter 4’s “runway.”

AD 1060: The Transition Point Where “the End of Regency Politics” Was Sealed

As confirmed in the macro-cycle volume, AD 1060 is the 270-year cycle’s 4th transition point. The tipping point arrives with Emperor Go-Sanjō’s enthronement in 1068 (+8 years).

Go-Sanjō was the first emperor in 170 years to ascend without Fujiwara maternal relatives. It was the first moment when “the imperial house pushed back, backed by warrior power.” The following year’s Enkyū Shōen Consolidation Decree (1069) directly attacked the regents’ economic base (shōen control).

Launch of Cloistered Rule (1086) — From “the End of Last Brilliance” to “the Birth of New Power”

In 1086, Emperor Shirakawa abdicated to become Retired Emperor and began cloistered rule. This was an entirely new power model: “abandoning the emperor’s title to seize real authority.”

📌 Meaning of the 26 Years from 1060 to 1086
AD 1060: 270-year transition — “the beginning of regency politics’ institutional end”
AD 1068: Emperor Go-Sanjō’s enthronement (tipping point, +8 years)
AD 1069: Enkyū Shōen Consolidation Decree (direct attack on the regents’ economic base)
AD 1086: Launch of cloistered rule (26 years after the transition)
→ “Regency politics ended” at the 1060 transition.
 ”The next power model (insei) launched” 26 years later in 1086.
 These 26 years were the transitional period of “dismantling the old order and groping for a new one.”

Section 1: The Triple Cycle Blueprint — Origin at 1060

Cycle Origin Node 1 Node 2 Node 3 Node 4
55-year AD 1060 1115 1170 1225 1280
83-year AD 1060 1143 1226 1309
90-year AD 1060 1150 1240 1330 (chapter end)
270-year macro AD 1330 (chapter end)
Key Discovery: The Triple Convergence of 1221–1240
55-year Node 3: 1225 → 4 years after the Jōkyū War (1221)
83-year Node 2: 1226 → 5 years after the Jōkyū War (1221)
(55-year and 83-year nearly simultaneous, 1-year gap)
↓ 14 years later
90-year Node 2: 1240 → 8 years after the Goseibai Shikimoku (1232)
270-year macro-cycle endpoint: AD 1330 = 90-year Node 3 (perfect alignment)

Section 2: Analysis of the 1st Period (1060–1143/1150) — The 55-Year Cycle “Brackets the Transitions”

1115 — 55-Year Node 1: “Full-Scale Launch of the Insei Economy”

The 55-year cycle’s Node 1 falls at 1115 — 28 years before the 83-year transition (1143) and 35 years before the 90-year transition (1150).

Around 1115, Emperor Toba had ascended (1107) 8 years earlier, and Retired Emperor Shirakawa’s cloistered rule was at its zenith. What was happening?

  • Retired Emperor Shirakawa was rapidly expanding the “imperial house’s directly controlled shōen network”
  • The transfer of “shōen economic hegemony from the Fujiwara regents to the imperial house” was nearly complete
  • Provincial warriors were becoming the retired emperor’s direct military force as “Hokumen no Bushi” (Palace Guards of the North)
📌 1115: “Full-Scale Launch of the Insei Economy”
Reading 1115 as the 55-year cycle’s “economic transition point,” it marks “the completion of economic hegemony transfer from the Fujiwara regents to the retired emperor, and the full-scale activation of cloistered rule as a new economic system.”
This pairs with the previous edition’s (origin AD 1024) interpretation of “1079: the transition point when the Fujiwara ceased to be the shōen economy’s hegemon.” The previous version captured “the end of regency economics”; the revised version captures “the beginning of insei economics” — two sides of the same transition.

1143 and 1150 — The 83-/90-Year Transitions and “the Eve of the Warriors’ Rise”

The 83-year Node 1 falls at 1143; the 90-year Node 1 at 1150. Within this 7-year gap, the transition “from the peak of cloistered rule to the rise of warriors” is compressed.

Year Transition Point Actual Historical Event Margin
1107 Origin + 47 years (before 55-year Node 1) Emperor Toba’s enthronement; Shirakawa’s insei continues (early eruption) Reference
c. 1115 55-year Node 1 Full-scale launch of insei economy (Hokumen warriors, direct shōen expansion) ±0 years
1129 55-year Node 1 + 14 years Toba’s insei begins in earnest (death of Retired Emperor Shirakawa) +14 years
c. 1143 83-year Node 1 Toba’s insei at its zenith; shōen accumulation reaches saturation ±0–few years
c. 1150 90-year Node 1 Run-up to Hōgen Rebellion (1156); warriors’ power becomes visible +6 years

The Hōgen Rebellion (1156) — “Insei Economy: From Saturation to Disintegration”

The Hōgen Rebellion came 41 years after the 55-year Node 1 (1115). Forty-one years after the “full-scale launch of the insei economy (1115),” the “transition point where the insei economy began disintegrating” arrived.

The structural problem of the insei economy was that “by using warriors, it made warriors’ power visible.” The Hōgen Rebellion was won by the side that “gathered more warriors.” From that moment, the fact that “warriors’ military power holds the ultimate say in politics” became public knowledge.

Section 3: Analysis of the 2nd Period (1143–1226/1240) — Completing the “Five-Chapter Triple Convergence”

In 1221–1226, the 55-year and 83-year cycles overlap within 1 year; in 1240, the 90-year cycle catches up. At that convergence point stands the Jōkyū War through the Goseibai Shikimoku — the era’s greatest turning point.

1170 — 55-Year Node 2: “The Establishment of the Taira Economic Model”

The 55-year Node 2 falls at 1170 — 3 years after Taira no Kiyomori was appointed Daijō-daijin (1167), in the middle of Kiyomori’s peak years (1167–1179).

Reading 1170 as an “economic transition point” reveals Kiyomori’s “new economic model based on Japan-Song trade” entering a stable trajectory. The circulation of Song coins centered on Fukuhara (modern Kobe) introduced an entirely new economic principle — “monetary economy and overseas trade” — fundamentally different from the shōen economy.

📌 Kiyomori’s Economic Model and the 55-Year Cycle
1167: Kiyomori appointed Daijō-daijin (3 years before 55-year Node 2)
c. 1170: Japan-Song trade “monetary economic model” enters stable trajectory (55-year Node 2)
1179: Kiyomori’s coup — Retired Emperor Go-Shirakawa’s insei suspended (9 years after Node 2)
1185: Battle of Dan-no-ura — Taira clan destroyed (15 years after Node 2)
→ The 55-year Node 2 (1170) was “the Taira clan’s economic zenith.”
 15 years later (1185), the Taira were destroyed.
 The 55-year cycle’s midpoint-reversal pattern — “decline begins immediately after the economic peak” — is confirmed here as well.

1221–1226: Jōkyū War to Goseibai Shikimoku — “The Chapter 4 Version of the Five-Chapter Pattern”

The 55-year Node 3 (1225) and 83-year Node 2 (1226) overlap within 1 year. Four to five years earlier (1221) comes the Jōkyū War; 8 years before the 90-year Node 2 (1240) comes the Goseibai Shikimoku (1232).

Transition Point Year Actual Historical Event Margin
55-year Node 3 (economic) 1225 4 years after Jōkyū War (1221) = post-war settlement completed −4 years
83-year Node 2 (civilizational) 1226 5 years after Jōkyū War (1221) = new order established −5 years
Actual transition event 1221 Jōkyū War (“the first time warriors reversed judgment on the court”) Lead
90-year Node 2 (power structure) 1240 8 years after Goseibai Shikimoku (1232) = warrior law established nationwide +8 years

The Jōkyū War (1221): A Triple Reading

On the surface, the Jōkyū War was “a coup in which Retired Emperor Go-Toba tried to overthrow the Kamakura shogunate and was defeated instead.” But reading it through the triple cycle reveals entirely different depths.

  • Read through the 55-year cycle (economic transition): “The final defeat of the insei-shōen economy and the decisive victory of the goon-to-hōkō (reward-for-service) economy.” After the war, Go-Toba was exiled to Oki, and many of the retired emperor’s shōen were transferred to jitō (warrior stewards).
  • Read through the 83-year cycle (civilizational transition): “Proof, broadcast nationwide, that the authority of emperors and retired emperors ‘cannot defy warriors.'” The unprecedented exile of an emperor fundamentally transformed the collective belief in “imperial authority.”
  • Read through the 90-year cycle (power-structure transition): “The establishment of governance by warrior law (Goseibai Shikimoku, 1232).” Replacing the ritsuryō (court law), an independent warrior legal system began to formally function.
📌 Why the Jōkyū War Lands at the “Five-Chapter Pattern” Location
At the point where “55-year + 83-year overlap within 1 year” across all five chapters, each era’s “most fundamental transition” arrives.
Chapter 1 (415–416): Emperor Yūryaku’s rise — “from chieftain coalition to personal autocracy”
Chapter 2 (685–686): Fujiwara-kyō — “completion of the ritsuryō system”
Chapter 3 (955–956): Post-Jōhei-Tengyō Rebellion economic/civilizational reordering
Previous Ch. 4 (1189–1190): Yoritomo’s shogunate officially recognized
Revised Ch. 4 (1225–1226): Post-Jōkyū War new order established
At the location where “civilizational transition (83-year) and economic transition (55-year) arrive simultaneously,” the “moment when the era’s governance principle fundamentally changes” always occurs. This is the law confirmed across five consecutive chapters.

Section 4: Analysis of the 3rd Period (1226–1330) — The 55-Year Cycle “Brackets the Mongol Invasions”

1280 — 55-Year Node 4: “Structural Limits of the Reward-for-Service Economy Exposed”

The 55-year Node 4 falls at 1280 — 1 year before the Kōan War (Second Mongol Invasion, 1281).

Around 1280, the Kamakura shogunate’s “goon-to-hōkō (reward-for-service) economy” had reached structural limits.

  • Both the Bun’ei War (1274) and Kōan War (1281) were “defensive wars”
  • Defensive wars produce no “new land” to distribute as rewards
  • Long-term Kyushu garrison duty (ikoku keigo banyaku) accelerated the gokenin vassals’ economic exhaustion
📌 The Mongol Invasions and the Collapse of the Reward-for-Service Economy
55-year Node 4 (1280): “The transition point where structural limits of the reward-for-service economy became visible”
For 48 years from the Goseibai Shikimoku (1232) to 1280, the warrior-law governance system functioned.
But its economic foundation (land redistribution) was rendered completely dysfunctional by “the Mongol invasions — purely defensive wars.”
The flow of “system completion (1232) → economic maturation (1280) → irreversible collapse” mirrors Chapter 2’s “Taihō Code (701) → economic maturation → rise of the shōen system” exactly.
Every governance principle follows the same path: “establishment → maturation → collapse.”

1297 — The Einin Tokuseirei: “A Failed Solution”

Seventeen years after the 55-year Node 4 (1280), the Einin Tokuseirei (Debt Cancellation Edict, 1297) was issued. This emergency measure to “cancel gokenin vassals’ debts” backfired when moneylenders (kashiage) stopped lending to gokenin entirely, freezing the economy. A textbook case of “debt cancellation producing credit collapse.”

1309 — 83-Year Node 3: “Seeds of the Shogunate’s Overthrow Are Sown”

The 83-year Node 3 falls at 1309 — 9 years before Emperor Go-Daigo’s enthronement (1318). Around 1309, autocratic rule by the tokusō (Hōjō main line) was intensifying, and “dissatisfaction among warriors” and “conflict with the court” were accumulating simultaneously.

1330 — 90-Year Node 3 and the 270-Year Macro-Cycle Endpoint in “Perfect Alignment”

The 90-year Node 3 falls at AD 1330. The 270-year macro-cycle’s 4th-period endpoint is also AD 1330.

Transition Point Year Actual Event Margin
90-year Node 3 AD 1330 Genkō War (1331) — the overthrow begins +1 year ✅
270-year macro endpoint AD 1330 Eve of the Kamakura shogunate’s fall (1333) +3 years ✅
Post 55-year Node 4 AD 1280 + 55 = 1335 2 years after the Kamakura shogunate’s fall (1333) −2 years ✅
📌 Chapter 4’s Closing “Triple Convergence”
Within the 3 years from AD 1330 to 1333, the triple cycle and the 270-year macro-cycle converged.
90-year Node 3 (1330) = 270-year macro-cycle endpoint (1330): perfect alignment
Genkō War (1331): the year after the transition
Kamakura shogunate falls (1333): 3 years after the transition
→ The law that “when micro- and macro-cycles converge simultaneously, history moves most dramatically” is confirmed at Chapter 4’s close (AD 1330), following Chapter 1 (AD 520), Chapter 2 (AD 790), and Chapter 3 (AD 1060). The same pattern repeats across four consecutive chapter endings.

Section 5: The Structural Law Revealed by the “Five-Chapter Consecutive Pattern”

The Mathematical Dimension

55×3 = 165; 83×2 = 166 — a 1-year gap. 90×2 = 180; the gap from 166 is 14 years. This is arithmetically inevitable. Therefore, “this pattern occurring every time” is mathematically guaranteed.

The question is: “Do those mathematical nodes coincide with historical turning points?”

The Historical Dimension — Five Consecutive Confirmations

Chapter Origin 55×3 83×2 Gap Historical Event at That Location
Ch. 1 AD 250 415 416 1 yr Emperor Yūryaku’s rise (embodiment of triple contradictions)
Ch. 2 AD 520 685 686 1 yr Fujiwara-kyō (completion of the ritsuryō system)
Ch. 3 AD 790 955 956 1 yr Post-Jōhei-Tengyō economic/civilizational reordering
Ch. 4 (prev.) AD 1024 1189 1190 1 yr Yoshitsune’s defeat + Yoritomo recognized (warrior governance established)
Ch. 4 (rev.) AD 1060 1225 1226 1 yr Post-Jōkyū War to Goseibai Shikimoku (warriors surpassed the court)
📌 Why Does History Move Most When “Civilizational + Economic Transitions Arrive Simultaneously”?
The 83-year cycle indicates transitions in “what people believe (ideas/civilization).”
The 55-year cycle indicates transitions in “how people live (economics/industry).”
When both transition simultaneously, dual pressure emerges: “old beliefs can no longer sustain even old ways of life.” If only one changes, it amounts to “the times are shifting.” When both arrive at once, society is forced into “fundamental redesign.”
Emperor Yūryaku, Fujiwara-kyō, the Jōkyū War, and the founding of the Kamakura shogunate — each can be read as “a moment when both beliefs and livelihoods changed simultaneously.”

Section 6: Complete Triple-Cycle Chronology (1060–1340)

Year 55-yr 83-yr 90-yr 270-yr Major Historical Events
1060 Origin Origin Origin 4th 270-year macro-cycle 4th transition point
1068 Emperor Go-Sanjō enthroned (tipping point, +8 yr)
1069 Enkyū Shōen Consolidation Decree
1086 Launch of insei — cloistered rule (Retired Emperor Shirakawa)
c. 1115 Node 1 Full-scale launch of insei economy
c. 1143 Node 1 Toba insei zenith; shōen accumulation saturates
c. 1150 Node 1 Run-up to Hōgen Rebellion; warrior power becomes visible
1156 Hōgen Rebellion (insei economy begins disintegrating)
c. 1170 Node 2 Japan-Song trade model stabilizes (Taira clan’s zenith)
1185 Battle of Dan-no-ura — Taira clan destroyed
1192 Yoritomo appointed Sei-i Taishōgun
1221 Jōkyū War (warriors reversed judgment on the court)
c. 1225 Node 3 Post-Jōkyū settlement completed; new order established
c. 1226 Node 2 Civilizational transition confirmed (imperial authority fundamentally transformed)
1232 Goseibai Shikimoku (governance by warrior law begins)
c. 1240 Node 2 Warrior law established nationwide (power-structure transition complete)
1274 Bun’ei War (First Mongol Invasion)
c. 1280 Node 4 Structural limits of reward-for-service economy exposed
1281 Kōan War (Second Mongol Invasion)
1297 Einin Tokuseirei (failed debt cancellation — credit collapse)
c. 1309 Node 3 Eve of Emperor Go-Daigo; seeds of overthrow sown
1318 Emperor Go-Daigo enthroned
c. 1330 Node 3 5th 270-year macro-cycle 5th transition / 90-year Node 3 (perfect alignment)
1331 Genkō War (overthrow begins)
1333 Kamakura shogunate falls

Section 7: New Discoveries from the Triple-Cycle Analysis

Discovery 1: The “Five-Chapter Consecutive Triple Convergence Pattern” Is Confirmed

With the starting point changed to AD 1060, the triple convergence pattern — “55×3 ≈ 83×2 (1-year gap) → 90×2 lags by 14 years” — is confirmed across five consecutive chapters, upgraded from four in the previous version.

The fact that a mathematical necessity (55×3 = 165, 83×2 = 166) “continues to align within 1 year of historical turning points” is the most powerful corroborating evidence for this cycle theory.

Discovery 2: The Jōkyū War Is “the Chapter 4 Transition Point of the Five-Chapter Pattern”

The previous version’s transition was “Yoshitsune’s defeat + Yoritomo’s recognition (1189–1190).” The revised version moves it to “Jōkyū War to Goseibai Shikimoku (1221–1232).” This shift is not merely a result of changing the starting point but “illuminates a more essential transition.”

Where Yoritomo was “recognized by the court,” the post-Jōkyū shogunate “surpassed the court.” The transition from “being recognized” to “surpassing” was the essence of this 270-year span.

Discovery 3: The Mongol Invasions Exposed “the Structural Limits of the Reward-for-Service Economy”

At the 55-year Node 4 (1280), “the structural limits of the reward-for-service economy became visible.” The problem that “defensive wars produce no rewards” existed before the Mongol invasions, but the invasions — “purely defensive wars” — made it a “visible problem.”

The economic narrative drawn by the 55-year cycle in Chapter 4: launch (1115) → the Taira monetary-economy challenge (1170) → establishment of the reward economy (1225) → structural limits exposed (1280) → irreversible collapse (1297) → shogunate falls (1333).

Discovery 4 (Revised Edition): Chapter 4’s Closing “Triple Convergence” — Four Consecutive Chapter-Ending Patterns

Within the 3 years from AD 1330 to 1333, the 90-year Node 3, the 270-year macro-cycle endpoint, the Genkō War, and the Kamakura shogunate’s fall all converged. Following Chapter 1 (AD 520), Chapter 2 (AD 790), and Chapter 3 (AD 1060), the same “chapter-ending triple convergence pattern” is confirmed for a fourth consecutive time.

“At the end of each 270-year period, the macro-cycle transition and micro-cycle nodes overlap, and history’s greatest upheavals occur” — this “chapter-ending law” has been confirmed across four consecutive chapters.

Conclusion — How the Triple Cycle Transformed Chapter 4’s Portrait

The original Chapter 4 (83-year + 90-year) was a political history of “from cloistered rule to the Kamakura shogunate — the establishment of warrior governance.” By adding the 55-year cycle and shifting the starting point to AD 1060, an economic history emerges behind that political narrative: “from the insei economy to the reward-for-service economy.”

The launch of cloistered rule (1086), the Taira clan’s Japan-Song trade (1170), the expansion of jitō control after the Jōkyū War (1221), and the post-Mongol debt cancellation edict (1297) — each is deeply intertwined with a 55-year economic transition point.

And the law confirmed across five consecutive chapters — “the greatest historical transitions occur where 55-year + 83-year transition simultaneously” — can be understood as the principle: “When civilization and economics change at the same time, society is forced into fundamental redesign.”

The 270 years of Chapter 4 (1060–1330) were the transitional period in which Japan moved from “an era under foreign governance principles (ritsuryō and Buddhism)” to “an era that created uniquely Japanese governance principles (warrior law and reward-for-service).” The economic foundation of that transition was the 55-year cycle’s narrative: “from the shōen economy to the reward economy, and the reward economy’s collapse.”

【Triple Cycle Detailed Analysis】Japan Edition — Chapter 4 Revised (AD 1060–1330)

⚠️ Disclaimer: This article is an analytical essay based on historical cycle theory and differs from academic historical research. Some correspondences with historical facts include points on which scholarly opinion varies.

📝 About the Author

Hiroshi Yamada / White & Green Co., Ltd.
Researcher of the 270-Year Historical Transition Cycle. Applied Monte Carlo analysis to data spanning 9 civilizations and 5,000 years, statistically demonstrating the 270-year historical transition period.

📄 Preprint: Yamada (2026) — OSF Preprints
DOI: 10.17605/OSF.IO/J9G8D

📝 About the Author

Hiroshi Yamada / White & Green Co., Ltd.
Researcher specializing in 270-year historical transition cycles. Applies Monte Carlo analysis to data spanning 9 civilizations and 5,000 years, statistically demonstrating a recurring 270-year historical turning-point cycle.

📄 Preprint (pre-peer review): Yamada (2026) — OSF Preprints
DOI: 10.17605/OSF.IO/J9G8D

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