Add 1600 checkpoint: Song Dynasty splits into North and South

Song civil war (~1600-1610s):
- Korean war aftermath → military seizes merchant assets → capitalist rebellion
- Military coups civil government → capitalists launch 靖难
- Result: permanent North-South split (Option C)
  - North: military junta, industrial base, puppet emperors (Dong Zhuo parallel)
  - South: capitalist-civilian regime, trade wealth, legitimate emperor, no heavy industry
  - Independent: Western Protectorate, Sichuan warlord, Vietnam/Burma autonomous

Malacca falls to Aceh (Ilkhanate proxy)
Japan: unifies, invades Korea twice, fails, likely isolates
Mongol Khanate: recovers mining rights from Song capitalists
Ilkhanate: biggest winner — may surpass Song as leading industrial power

Plantagenet France: religious wars resolved, Scotland split (Lowlands→England, Highlands→Paris)
American colonies: condominium arrangement
Italy: scientific revolution begins, independent innovation

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

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-## Open Questions (Post-1575 Chronological Development)
-
-1. **Song**: When does the Eastern Han mode end? Next fragmentation or reform?
-2. **Ilkhanate vs Song**: Malacca Wars — does the Ilkhanate ever take it? Or permanent stalemate?
-3. **England**: When does coal/iron industrialization trigger the next political crisis?
-4. **Japan**: Who unifies? What orientation?
-5. **Great Khanate**: Does the coup-reform buy enough time? When does Poland leave?
-6. **Americas**: New World silver's long-term impact on global economy?
-7. **Egypt**: Does it finally fully break away from the Ilkhanate?
-8. **India**: Post-unification — Timurid-India as great power or Song economic dependency?
-9. **Remaining to 1836**: 261 years, ~10 checkpoints
+## 1600 Checkpoint: Song Dynasty Splits
+
+### Japan Unification and Korean Invasion (~1590s-1600s)
+- Tokugawa-equivalent unifies Japan (Sekigahara ~1600). Technology slightly more advanced than our timeline (multiple foreign weapon sources during Sengoku).
+- Unified Japan launches Korean invasion (~1592 equivalent) → Song military junta sends troops → Japan repelled (~1598)
+- **Song troops remain in Korea after the war** → military officials seize Song merchant assets (mines, trading posts) in Korea
+- **This triggers the Song political crisis**: capitalist class vs military junta
+
+### Plantagenet France: Religious Wars + Scotland
+- **Religious wars** (~1580s-1600s): Catholic Paris court vs Protestant English nobles + continental minority Reformed communities
+- **Resolution**: Nantes-equivalent edict of tolerance. English religious autonomy confirmed. Continental Protestantism tolerated.
+- **Scotland conquered**: Lowlands under English Parliament jurisdiction, Highlands under French direct rule. **Both sides unhappy** — English want all of Scotland, Paris wants all of Scotland.
+- **American colonies**: Cannot be assigned to either English Parliament or Paris crown → **condominium** (joint administration, like Austria-Hungary's Bosnia). Inefficient but avoids split.
+
+### Burgundy
+- Religious tensions resolved through tolerance edict (too small for civil war)
+- Continues balancing between Germany and France
+
+### Italy: Scientific Revolution
+- Centuries as Song goods gateway → accumulated technical knowledge now generating **independent innovation**
+- Galileo-equivalent scientists: astronomy, mechanics, optics
+- Europe developing scientific tradition independent of Song
+- Significance for V3: European innovation capacity will help close the technology gap with Song
+
+### Song Dynasty Civil War and Split (~1600-1610s)
+
+#### Escalation
+1. (~1598) Military seizes merchant assets in Korea → capitalist fury
+2. (~1600s) Capitalists fund civil officials to challenge military → civil officials attempt reforms
+3. Military **coups**: deposes civil government, puppetizes emperor
+4. Southern capitalists declare **靖难**: "court usurped, we restore legitimacy"
+
+#### The Split: Two Songs
+
+**Northern Song (北宋, military junta):**
+| Territory | Status |
+|---|---|
+| Yan/Beijing industrial zone | Core — factories, heavy industry |
+| Liaodong/South Manchuria | Industrial + mining heartland |
+| Northern Central Plains | Agricultural/industrial |
+| Hexi Corridor + Western Protectorate | Nominally under North, actually independent warlords |
+| Korea | Military garrison (useful — repels 2nd Japanese invasion) |
+- Emperor: puppet, repeatedly deposed and replaced by military strongmen (**Dong Zhuo parallel** — warlords use imperial title as legitimacy tool)
+- Has: factories, armies, weapons production, heavy industry
+- Lacks: money, trade fleet, export markets, political legitimacy
+
+**Southern Song (南宋, capitalist-civilian regime):**
+| Territory | Status |
+|---|---|
+| Jiangnan (Hangzhou?) | New court, economic center |
+| Fujian / Guangdong | Maritime trade bases |
+| Huguang / Jiangxi | Agricultural heartland |
+| Sichuan | Nominally South, actually warlord |
+| Yunnan → Burma corridor | Nominally South, functionally autonomous |
+| Vietnam | Nominally South, fully localized |
+| Australia settlements | Southern migrants, small but growing |
+- Emperor: legitimate succession claim (brother/son of previous emperor). Real legitimacy.
+- Has: money, ships, trade networks, Southeast Asian connections, foreign arms purchases, legitimacy
+- Lacks: heavy industry, large standing army, weapons factories
+
+**Independent / Autonomous after the split:**
+| Entity | Status |
+|---|---|
+| Western Protectorate | Fully independent warlord state (Hexi + E. Xinjiang). Nominally acknowledges North. |
+| Sichuan | Nominally South, actually autonomous warlord |
+| Vietnam / Burma | Nominally South, fully localized / independent |
+| SE Asian Chinese polities | Further fragmentation, many fully independent |
+| Aceh Sultanate | Seizes all of Aceh island + **occupies Malacca** (on behalf of Ilkhanate Shia alliance) |
+
+#### Why Neither Side Can Win Quickly
+- North: can't reach South's maritime empire (no navy), can't cut off sea trade
+- South: can't match North's industrial army on land, can't take factories by force
+- → **Prolonged stalemate → permanent split** (like historical Northern/Southern dynasties)
+- By V3 era (1836): two separate Song states, 236 years of separation — longer than historical North-South dynasties (420-589)
+
+### Japan: Second Korean Invasion Fails
+- Unified Japan tries again during Song chaos → but Northern Song's Korean garrison is still functional
+- Japan repelled again → likely leads to Tokugawa-equivalent isolation policy (futility of continental expansion proven)
+
+### Mongol Khanate: Recovers Mining Rights
+- Northern Song regime supports Mongol Khanate reclaiming mines (the capitalists who owned them are now the enemy in the South)
+- Song economic colonization of Mongolia partially reversed
+- Mongol mining now under local control → continued industrialization but with Mongol ownership
+
+### Ilkhanate: Strategic Windfall
+- Song split = Ilkhanate's greatest strategic opportunity in centuries
+- Malacca taken (via Aceh proxy) → controls Indian Ocean → Pacific chokepoint
+- Can sell industrial goods to Southern Song (which has money but no factories)
+- Indian Ocean dominance increases
+- May surpass Song as world's leading industrial power during this period
+
+---
+
+## 1600-1625: The Economic Shockwave (TO BE DISCUSSED)
+
+The world's largest industrial economy just split in half. Every country that traded with Song is affected. Global supply chains disrupted. Commodity prices in chaos. The Ilkhanate, Germany, and Portugal positioned to fill the vacuum.
+
+Key questions:
+1. How does Southern Song survive without heavy industry? (Import from Ilkhanate/Germany?)
+2. How does Northern Song survive without trade revenue? (Autarky? New markets?)
+3. Who fills Song's role as global industrial goods supplier?
+4. What happens to global silver/currency flows?
+5. How do SE Asian states respond to the power vacuum?
+
+---
+
+## Open Questions (Post-1600)
+
+1. **Song split consequences**: Economic shockwave, global trade realignment
+2. **Ilkhanate**: Does it become the world's leading industrial power?
+3. **England**: Coal/iron still dormant — when does it industrialize?
+4. **Americas**: Portuguese empire + New World silver + Song disruption = ?
+5. **Great Khanate**: Effect of Song split on its eastern frontier?
+6. **India**: Timurid-India response to Song split?
+7. **Remaining to 1836**: 236 years, ~9 checkpoints