First released as a DOS game in 1993, Aces of the Deep quickly established itself as my favorite subsim. AOD was upgraded and improved in 1995, released as Command Aces of the Deep. It is intended as a historically accurate WWII U-boat simulation, with very little left out. Where many sims have one foot in the game category, Command Aces is pure sim. The three mission formats, single, historical, or the challenging career mode are present. You can start off at the outset of the war and you’ll be assigned a Type II boat with meager capabilities and range and only two forward tubes (six torpedoes). But the escorts are none too intimidating at this point, so your deficiencies are nicely balanced. From September 1939 until well into the early forties you’ll encounter many lone merchants–easy pickings! But in perfect accordance with historical precepts, from 1943 on the going gets tough and the convoys are well escorted by destroyers and corvettes with radar. In May 1943 you will be besieged by radio messages from fellow U-boats telling of attacks by aircraft and destroyers (Attacked by aircraft. . . sinking. . . U-344), and you get the sense that now the hunters have become the hunted.