Add 1475 checkpoint: Song dynasty crisis erupts, global ripple effects

Song Dynasty crisis (~1460s-1470s):
- Second cold wave triggers multi-directional fragmentation
- Southern peasant revolts, northern military takeover, Western Protectorate independence
- SE Asian colonies loosening, Korea recovering autonomy
- Dynasty persists in name but power fragmented (late Han/Tang parallel)
- Industrial production continues under military control — tech lead not lost

Global effects:
- Ilkhanate enters golden age, exploits Song distraction for Indian Ocean expansion
- Great Khanate accelerating decline (Northern Ulus near-independent, Poland/Byzantium loosening)
- Portugal: Atlantic direction confirmed, Columbus approaching
- Aragon: first North African outposts
- Plantagenet France: English nationalism emerging
- Burgundy: absorbed W. Lorraine, expanding toward Savoy
- Religious reform: printing press accelerating, formal Reformation likely within 25-50 years

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

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-## Open Questions (Post-1450 Chronological Development)
-
-1. **Song's North-South crisis (~1460-1500)**: How does it play out? Civil war? Peaceful restructuring? Western generals' role?
-2. **Columbus discovers Americas (~1490s)**: Portuguese colonization of the New World — what develops?
-3. **Reformation**: Hussite movement → when does it become a full break from Rome?
-4. **Ilkhanate industrialization**: Does it succeed? How does it change the global power balance?
-5. **Aragon as great power**: How far does it expand? North Africa? More of Italy?
-6. **Timurid-India unification**: Does it succeed? How does Song respond?
-7. **Great Khanate**: Stabilization or continued decline?
-8. **East Africa**: Song vs Portugal vs Ilkhanate — three-way colonial competition?
+---
+
+## 1475 Checkpoint: Song Dynasty Crisis
+
+### Song: Multi-Directional Fragmentation (~1460s-1470s)
+Second cold wave (Spörer Minimum, ~1460+) hits the same structural weaknesses exposed 100 years earlier, but now with no remaining buffers.
+
+**What breaks:**
+- **Southern peasant revolts** (~1470): Famine + unemployment + White Lotus-type religious movements. Multiple provinces (Jiangxi, Huguang, Fujian). Multiple rebel leaders, no unified movement.
+- **Northern military officials** summoned to suppress revolts → use this as military takeover. Court becomes puppet.
+- **Western Protectorate** (Xinjiang military governors): sees central authority collapse → declares de facto independence. Controls Hexi Corridor + eastern Xinjiang. Silk Road transit taxes become their own revenue.
+- **SE Asian colonial governors**: begin acting independently (metropole too distracted to enforce control). Chinese settler polities in Borneo/Sumatra may fully detach.
+- **Korea**: Song's grip loosens → may recover substantial autonomy.
+
+**1475 status**: Song dynasty NOT destroyed — the name, emperor, and institutions persist. But actual power fragmented:
+- **North**: Military junta controls industrial heartland (Yan, Manchuria south, Hexi approaches). Industry continues operating (the generals need it).
+- **South**: Revolts suppressed but resentment seethes. Landlord class intact. Economy devastated.
+- **West**: Independent military governors in Western Protectorate.
+- **Overseas**: SE Asian empire loosening, individual governors/settler states gaining autonomy.
+- Parallel: late Eastern Han, late Tang, or late Qing — dynasty exists in name, real power elsewhere.
+
+**What does NOT break**: Industrial production. Northern factories keep running under military control. Song's technological lead is not lost — it's just wielded by generals instead of the court. Trade continues (everyone needs the revenue). The Song "brand" for industrial goods remains globally dominant.
+
+### Global Ripple Effects of Song Crisis
+| Affected entity | Impact |
+|---|---|
+| Ilkhanate | Relative advantage increases; accelerates Indian Ocean expansion while Song is distracted |
+| Western Protectorate | De facto independent; controls Silk Road eastern segment |
+| SE Asian colonies | Fragmentation; Chinese settler states become autonomous |
+| Korea | Recovers some autonomy as Song mining oversight weakens |
+| Mongol Khanate | May escape economic colonization (Song capital/attention withdrawn) |
+| Japan | Silver exports more critical (supply chain uncertainty drives up precious metal demand) |
+| Portugal | Eastern trade system unstable → Atlantic direction even more attractive |
+| Ilkhanate Indian Ocean | Expands trading posts in India/East Africa without Song competition |
+
+### Great Khanate: Accelerating Decline
+- Second cold wave hits Ukraine/Hungary agriculture → serf unrest, sporadic revolts
+- **Northern Ulus**: nearly independent now. Finnish war credentials + Baltic trade revival = autonomous khanate in all but name.
+- **Poland**: szlachta expanding privileges, Catholic identity strengthening, watching for opportunity
+- **Byzantium**: quietly gaining autonomy, Constantinople Orthodoxy vs Volga Orthodoxy split deepening
+- Great Khanate's effective control shrinking to Volga-Ukraine-Hungary core
+
+### Ilkhanate: Golden Age
+- Industrial development advancing (early factories in Isfahan, Tabriz — Persian textile modernization, metallurgy)
+- **Exploiting Song's distraction**: expanding Indian Ocean trading posts (Gujarat, Malabar, East African Swahili coast)
+- Egypt: governor's double game continues, increasingly autonomous
+- Shia Islam spreading further along Indian Ocean trade routes (Aceh solidifying as Shia sultanate)
+- May be the world's most dynamic economy at this moment (Song's crisis + Ilkhanate's trade position)
+
+### Europe: Steady Development
+- **Greater Germany**: Constitutional compromise achieved (elected federal leader). Proto-industrial development via Song technology imports. Internal stability improving.
+- **Aragon**: Mediterranean empire consolidated (Barcelona to Naples). Beginning to establish first North African coastal outposts (Tunisian/Algerian coast).
+- **Plantagenet France**: Scotland Lowlands occupied, Highlands resist. **English nationalism emerging** — island elites resent Paris court's neglect/taxation. First serious unrest or petition movement.
+- **Burgundy**: Western Lorraine absorbed. Influence extending toward Savoy. Dijon flourishing as French-language cultural capital. "True France" narrative maturing.
+- **Castile**: Recognizing it's falling behind. Beginning Atlantic exploration but a generation behind Portugal.
+- **Portugal**: Deep into African coast (past Gulf of Guinea). Cape Colony developing. Columbus arriving in Lisbon (~1477). Western voyage being planned.
+- **Kalmar Union**: Vinland developing from seasonal camps to small permanent settlements. Cod fishing economy growing. Northern Ulus conflict ongoing.
+
+### Bohemia + Religious Reform
+- Printing press (since ~1440s) mass-producing reform pamphlets
+- Hussite-type ideas spreading across German, Burgundian, and even French territories
+- Papacy cracking down but losing the information war
+- **Formal Reformation break likely within ~25-50 years** (earlier than historical 1517)
+
+### India
+- Timurid-Indian Empire launching Deccan campaigns (southward expansion)
+- Song economic penetration via Burma Road continues despite Song's internal crisis (trade is decentralized, merchants keep trading)
+- North Indian textile industry severely damaged by Song imports
+- Vijayanagara Empire in the south: last major holdout against both Timurid military and Song economic pressure
+
+---
+
+## Open Questions (Post-1475 Chronological Development)
+
+1. **Song resolution**: Does the crisis resolve? New dynasty? Constitutional reform? Permanent fragmentation?
+2. **Columbus (~1490s)**: Portuguese discovery of Americas — immediate consequences?
+3. **Reformation (~1500?)**: Formal break from Rome — who leads it? Germany? Bohemia? France?
+4. **Ilkhanate**: Does it achieve full industrialization? When?
+5. **Great Khanate**: When does it lose Poland/Byzantium/Northern Ulus?
+6. **English separatism**: Does England break from Plantagenet France?
+7. **Timurid-India**: Does unification succeed?
+8. **1836 world**: We're now 360 years from V3 start — what's the trajectory?