A scenario editor and assembly language source code for the game were also sold by APX as separate products.

The player commands German units at the corps level as they invade the Soviet Union in 1941 and fight the computer-controlled Russians.

Eastern Front is a corps-level simulation of the first 41 weeks of Operation Barbarossa, the German invasion of the Soviet Union in 1941.

Units are represented as boxes for armored corps or cavalry, and crosses for infantry, an attempt to replicate conventional military symbols given the low resolution.

[4][5] The map covers the area from just north of Leningrad at the top to Sevastopol at the bottom, and from Warsaw on the left to just east of Stalingrad on the right.

[7] When autumn begins on 5 October 1941 and the green land changes to purple-brown mud, the player is likely losing if they have not captured most objectives, destroyed most early Russian forces, and established a defensive position.

[7] A high score by early autumn is not difficult but keeping it high during winter is almost impossible, as mud and snow appears, rivers and land gradually freeze during winter,[2] and Russians counterattack;[7] until the spring thaw the German side is forced into a purely defensive role.

If the player survives until spring the season offers a renewed offensive capability, but only for a short period before the game ends.

In an example of pondering, the computer AI calculates its moves during the period between vertical blank interrupts (VBI).

[2] Because of iterative pondering, the computer's moves become better the longer the player waits before issuing orders each turn, and a tactic that works well in one game might be less effective in another.

The tactical part of the AI attempts to intercept these movements, sending its mobile forces first one way, then the other, never actually making contact.

This results in the computer forces clumping up in front of the Germans, allowing the wings to move in once motion was difficult.

After writing Tanktics, which simulated German and Soviet tank battles during World War II,[13][14] Crawford wrote the first version of what he called Ourrah Pobieda (Russian for "Horray, Victory!")

[16] He was reportedly most proud of the iterative pondering, and stated that Eastern Front only uses 75% of Atari 8-bit graphic capabilities.

[7] Renamed Eastern Front shortly before release, APX began selling the game in August 1981.

[20] Crawford stated in 1987 that the game had been the most lucrative for him "by at least a factor of four",[16] and in 1992 that it had sold "fabulously well—far better than anybody (myself included) expected", with most purchasers not traditional wargamers.

To improve the gameplay he revamped the AI code, and eliminated the ability to "fast forward" the game and avoid combat.

In the highest level, "expert", air force corps (Fliegercorp) are added, and the units can be placed in one of several modes; normal, assault, or defend and move.

In "expert" the user can also choose to start in either 1941 with the standard opening, or 1942, with fully developed lines deep within Russia.

The review praised the graphics and the artificial intelligence, noted its pondering, and suggested that the game was a killer app for Atari computers.

[6] While the game was still being sold, Crawford released its source code through APX as a separate, commercial product targeted at developers.

Legionnaire uses the same map engine to simulate the Roman legions fighting the barbarians, but modifies it to move units in real time.