Add 1625 checkpoint: economic shockwave, Americas, Egypt expansion, global survey

Economic shockwave from Song split:
- Global industrial goods supply dropped 40-60%
- Ilkhanate surpasses Song as #1 industrial producer (~1620s)
- Germany/Bohemia/Portugal/Italy fill European vacuum
- Industrial production permanently multipolarized

Americas detailed: Portuguese empire (Mexico, Peru, Brazil, Caribbean), Castile (secondary),
Kalmar Vinland (225yr fishing/trade settlements), French/English (early), German (growing)

Egypt dual expansion: Red Sea → East African colonization + westward Sunni alliance building
Independence trajectory: economic base + diplomatic network → formal break ~1650-1700

Japan: isolation + Hokkaido colonization
India: unified, economic dependency shifted from Song to Ilkhanate
Mongol Khanate: nationalized Song mines, modest industry, reached Bering Strait
Great Khanate: reform failing, serfdom blocks industrialization, Ukraine famines
North-South Song: active Three Kingdoms-intensity war along Yangtze line

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

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 ---
 
-## 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
+## 1625 Checkpoint
+
+### North-South Song: Active War (~Three Kingdoms intensity)
+- Not a frozen conflict — active campaigning along the Yangtze/Huai River line
+- Similar to Three Kingdoms period in scale and intensity: major battles, shifting frontiers, but neither side can deliver knockout blow
+- North has industrial army but no navy; South has money and ships but weak land forces
+- Yangtze River as approximate boundary (historical pattern for all Chinese north-south splits)
+- **Both sides industrially active**: North has legacy factories, South rebuilding (industrialists fled south, ~25 years to rebuild → by 1625 Southern Song has functioning industry)
+- War drives innovation on both sides (military necessity)
+
+### Global Economic Shockwave (1600-1625)
+- Global industrial goods supply dropped ~40-60% from Song split
+- **Winners** (filling the vacuum):
+  - Ilkhanate: may have surpassed Song as world's #1 industrial producer by ~1620s
+  - Greater Germany + Bohemia: European industrial leaders, filling European market vacuum
+  - Portugal: colonial industry expanding
+  - Italy: science revolution + manufacturing = new industrial center
+- **Losers**:
+  - India: economic dependency shifts from Song to Ilkhanate
+  - Korea: war zone, mining disrupted, becomes Northern Song's resource colony
+  - SE Asia: fragmented, economies in recession
+- **New global order**: Industrial production multipolarized permanently. Even if Song reunifies, the monopoly is broken forever.
+
+### Americas (~1625)
+**Portuguese Empire** (130 years of colonization):
+- Mexico (New Portugal): Mexico City ~150,000. Silver mining. Colonial aristocracy. Catholic Church. Native population crashed ~90%.
+- Peru: Potosí silver at full production. Lima administrative center. Forced labor system.
+- Brazil: Sugar plantations (northeast), African slave labor. Expanding.
+- Caribbean: Sugar + tobacco + slave trade hub.
+- Total: ~30-50k Europeans, ~20-30k African slaves, millions of mestizo/native.
+
+**Castile**: Secondary American power. Río de la Plata, Venezuela, Pacific coast scraps. Much smaller than Portugal.
+
+**Kalmar Vinland** (225 years): Newfoundland → Nova Scotia → New England coast. Cod fishing, timber, fur trade. ~10-30k settlers. Gradual contact with natives (less catastrophic disease impact than southern conquest model).
+
+**Plantagenet France / English**: North American mid-coast (Virginia equivalent). Condominium administration. Small, early. Tobacco starting. English nobles may view colonies as escape from Paris control.
+
+**Greater Germany**: Increasingly active in Caribbean (trading posts, small islands) and West Africa. Hanseatic capital funding expansion. Hamburg/Bremen as Atlantic bases. **More aggressive American participation than previously assumed** — large population base supports colonization.
+
+**Mongol Khanate**: Reached Bering Strait area but **no settlement motivation** — sparse population has no push factor for trans-Pacific colonization. Awareness of American landmass exists.
+
+### Japan: Isolation + Hokkaido
+- Tokugawa-equivalent establishes isolation policy after two failed Korean invasions
+- Limited trade through designated ports (Nagasaki equivalent?)
+- **Actively colonizing Hokkaido**: expanding into Ainu territory (closest frontier, doesn't require navy)
+- Silver economy adjusting to New World competition — declining but not collapsed
+
+### Timurid-Indian Empire: Unified India
+- Unification of subcontinent complete (or nearly so). Akbar-equivalent golden age.
+- **Economic dependency shifted from Song to Ilkhanate**: Indian handicraft industry destroyed by Song imports, now imports Ilkhanate industrial goods instead. New master, same dependency.
+- Massive population, agricultural wealth, but industrially hollow.
+- Song's Burma Road connection disrupted by split → India has more economic breathing room?
+
+### Mongol Khanate: Unexpected Beneficiary
+- **Nationalized Southern Song mining operations** after the split (capitalist owners fled south, Northern Song regime supported Mongol reclamation)
+- Now has **state-owned industrial capacity**: mining, processing, limited manufacturing
+- Industrial level: modest but real — more than just resource extraction now
+- Still sparse population, but per-capita modernization significant
+- Reached Bering Strait / awareness of American continent (but no settlement motivation)
+- **Relationship with Northern Song**: complex — both post-Song military states, possible allies of convenience
+
+### Egypt: Dual Expansion
+**Eastward — Red Sea → East Africa colonization:**
+- Egyptian ships from Red Sea ports → Aden → Horn of Africa → Somali/Kenyan coast
+- Independent of Ilkhanate's Persian Gulf → Swahili coast route
+- Egypt controls northern Swahili coast; Ilkhanate controls southern; Portugal furthest south
+- Builds Egypt's independent economic base (not dependent on Ilkhanate trade system)
+
+**Westward — Sunni Alliance Building:**
+- Al-Azhar scholars dispatched to North African states (Tunisia, Algeria, Morocco)
+- Building a Sunni diplomatic/religious network
+- "Shared threats" narrative: Shia Ilkhanate from east, Catholic Europe from north
+- **Tension with Hafsid Tunisia**: both claim Sunni leadership (Al-Azhar vs. Hafsid Caliphate). Competitive cooperation — rivals who must ally against common threats.
+- Goal: Sunni bloc from Morocco to Egypt, providing diplomatic/military backing for eventual full independence from Ilkhanate
+
+**Independence trajectory**: Economic base (East Africa) + diplomatic network (Sunni alliance) + military autonomy (own army) building toward formal break. Timing: possibly ~1650-1700.
+
+### Great Khanate: Attempted Industrialization
+- Post-coup reformist Khan (Northern Ulus origin) attempting modernization
+- **Serfdom blocks industrialization**: forced labor eliminates mechanization incentive
+- Maunder Minimum approaching → Ukraine/Hungary crop failures → serf conditions worsening
+- Repeated Ukrainian famines → sporadic uprisings (suppressed but destabilizing)
+- Poland: szlachta parliament powers still expanding
+- **Industrial imports disrupted by Song split** → Great Khanate's technology modernization stalls
+- The reformist agenda is failing: surface Europeanization without structural change
+
+### West Africa: Escalating Competition
+- Songhai Empire: possibly surviving (Morocco too weak to invade in this timeline, and Songhai may have fire weapons)
+- Coastal scramble intensifying: Portugal (dominant), Germany (growing), Castile, Aragon, France, Morocco all competing
+- **North Africa's tech level comparable to southern Europe** — not the helpless targets of our timeline's colonialism
+- Slave trade: major and growing (demand from American plantations)
+
+### Western Protectorate
+- Fully independent warlord state (Hexi + eastern Xinjiang)
+- Nominal acknowledgment of Northern Song but functionally sovereign
+- Limited activity: maintains Silk Road segment, occasional trade, self-preservation
+- Northern Silk Road has no advantage over sea/southern routes → economically marginal
+
+### Ilkhanate Constitutional System Update
+- "Austro-Hungarian" model functioning: Persian core + Egyptian autonomy
+- Egyptian Majlis increasingly assertive
+- Sunni ulama in the guardian council creating a more pluralist religious framework
+- But tensions building: Persian industrial interests vs Egyptian agricultural/colonial interests
+- East African colonization creating jurisdictional disputes (whose colony is it — Egypt's or the Empire's?)
+
+---
+
+## Open Questions (Post-1625)
+
+1. **Silver inflation**: Global impact of 80+ years of Potosí + Song split disruption?
+2. **Maunder Minimum** (~1645-1715): Coldest period — agricultural crisis everywhere. Who suffers most?
+3. **Egypt independence**: When? How does Ilkhanate respond?
+4. **Song reunification**: Does it ever happen? Or permanent split through V3?
+5. **England industrialization**: Coal/iron awakening — when?
+6. **Great Khanate**: Does serfdom reform happen or does the empire continue declining?
+7. **Remaining to 1836**: 211 years, ~8 checkpoints