Hearts of Iron II: Doomsday is a stand-alone expansion for the game of World War II strategy, Hearts of Iron II, released in April 4, 2006. It contains everything that was in the original game while highlighting and expanding the period after historical World War II, including a hypothetical nuclear war between the Soviet Union and the Allies.
There is a new intelligence sub-game for spies. This provides information on other countries and allows operations against them such as:
- Steal Technology Blueprints
- Sabotage Production
- Assassinate ministers and leaders
- Spread propaganda
- Talk to the mass media
- Sabotage infrastructure
- Fund partisans
Doomsday also features some other changes and additions such as:
- Additional graphics such as bomber sprites
- Escort Carriers (CVL)
- Hospital technology tree that recover manpower losses
- A "do not upgrade" button for divisions (much requested by fans)
- The option of automating the production sliders (much requested by fans)
- Submarines have separate stats for convoy raiding and naval combat
- An extended timeframe - the game end date has been changed to 1953
- New technologies to bring the game into the cold war era
- An included scenario editor
- The ability to trade divisions between nations
- Minister and tech effects such as small arms assembly apply to existing serial runs. You no longer have to restart serial runs to get the benefits.
- Factory and other province improvements [forts] production times finish on the same day regardless of any infrastructure differences.
- The upgrade portion of the Army slider was changed. Upgrade cost and time is cut in half. In HOI2 it was 10 to 100 in increments of 10 while in Doomsday it's 5 to 50 in increments of 5.