Hearts of Iron 2: Doomsday Armageddon is a booster pack for Hearts of Iron 2:Doomsday.
The main addition was mostly for 2 new scenerio's designed for Online, it includes 11 nations all equally strong and each one has an intresting backstory as to how the nation came to be using alternate history.
Other changes include extending the timeline up to 1964, and included a lot of new options for gameplay such as the ability for countries to absorb other countries tech teams.
It is a small expansion and therefore is a small price, it is not required the best gameplay experience but the latest patches use Armageddon so for the biggest improvement for gameplay balance it is recconmended you pick it up.
Windows 98SE / 2000 / XP
Processor: Pentium III 800 MHz
Memory: 128 Mb RAM
Hard disk space: 1 GB Free Hard Drive Space
Video: 4 MB Video Card DirectX Compatible
Sound: Direct X-compatible sound card
DirectX®: DirectX 9