The Empire and the Union are in the midst of a long-standing war, and it seems that a ceasefire is to take place soon. However, just days before the ceasefire, the Union prepares new weapons and gears up for more combat, forcing the Empire to fight back.
The game plays like a typical vertical shooter with 3D graphics and a tilted perspective, with a few twists. When not firing, you can tilt your helicopter up to about 30 degrees in either direction to fire at offset directions. You also have an Option that can be charged up by releasing the fire button and letting the Option gauge fill up, at which point the Option will seek out and fire at targets for bonus points; your Option can alternate between three different types (gun, cannon, rocket) through powerups.
In 2012, G.rev released Under Defeat HD on PlayStation 3 and Xbox 360. Under Defeat HD is an Updated Re-release featuring a new mode, the New Order mode, which uses a 16:9 game window, adds a few more tweaks such as dual-analog controls, and features an arranged soundtrack. Under Defeat HD was released in Japan, the United Kingdom, and North America (on PS3 only) in 2012, throughout the rest of Europe in 2013, and in North America on Xbox Games on Demand in 2014.
Under Defeat provides examples of the following:
- 2½D: Helicopter movement (relative to the screen) is in two dimensions, but visuals are rendered in 3D. Additionally, shots from ground targets take time to reach your altitude, and your center gun will adjust to hit targets on the ground.
- The Alliance: The Union. Unusually, the Union serves as an antagonist force.
- Arcade-Perfect Port:
- The Dreamcast port, naturally, as the Dreamcast's hardware matches the Sega NAOMI's.
- The same cannot be said for the HD ports in arcade mode; while they are mostly are mostly accurate, there are some differences such as timing differences in enemy appearances and attacks, as well as a wealth of slowdown on the Final Boss not seen in the NAOMI or Dreamcast versions, especially with the game in vertical-monitor mode.
- Battleship Raid: There are several battleships in Stage 2, but the most notable one is the massive boss battleship that serves as the boss.
- Cap: You can have up to six bombs; collecting excess bombs will grant you 10,000 points each.
- Charged Attack: The Option is charged up by releasing the fire button until the gauge fills up with green, and then firing again. After the Option is either shot down or runs out of ammunition, it has a cool down period before it can be charged up again.
- Dynamic Difficulty: The game has a "rank" system, but how it works is largely a mystery to even experienced players.
- The Empire: The Empire. Unusually, you play as plots hailing from it.
- The Empire is a stand-in for Nazi Germany, with the pilots' uniforms and use of German reflecting this.
- The Union is a fusion of World War II Allied and non-German Axis powers.
- Good Republic, Evil Empire: Inverted. This time, the Union are the bad guys while the Empire is good.
- Hard Mode Filler: Complete all five stages with an average Contribution rating of 95% or higher to access the second loop.
- Long Song, Short Scene:
- The arranged versions of the original tracks have extra sections, and most likely in a given stage you won't get to hear the whole track unless you pause the game.
- The New Order stage 1 track, "Don't look back!", has a breakdown section at the end of the track that is not heard if, again, you don't pause the game, even if you time out the endboss.
- Nintendo Hard: It's an Arcade Game, so it has to be. And since you don't get extra lives, there is not much room for error.
- 1-Up: Averted. There are no extra lives at all, so make every last life count!
- Putting on the Reich: The Empire is effectively the Nazis in all but name. In a twist on this trope, you're fighting for the Empire.
- Scoring Points: In addition to the standard "kill enemies for points" formula, there are a few gimmicks. More information can be found here, but here's the gist of it:
- Destroying an enemy with your Option doubles the point value of that enemy.
- At the end of each stage, you get some bonuses: the "Contribution" bonus for destroying specific targets within the stage, the timer bonus, and the bombs remaining bonus.
- Surprisingly Good English: Spoken by those on the side of the Union.
- Surprisingly Good Foreign Language: German, spoken by those on the side of the Empire.
- Silence Is Golden: Stage 5, which is the ruins of a major city, begins with a somber track and no sound effects, before the track picks up and the sound effects come back.
- Smart Bomb: Three per life, with more obtainable through bomb pickups.
- Tank Goodness: A large plurality of enemies, especially ground enemies, comprise tanks.
- This Is Not a Drill: Spoken verbatim by a loudspeaker in Stage 2, as an order to Union forces:"Enemy attack! Battle stations, battle stations! All hands to battle stations! This is not a drill! I say again: This is not a drill!"
- Time-Limit Boss: Each boss is on a timer. You get 1,000 points for each whole second left on the timer when the boss is defeated. Timing out the boss will cause it to self-destruct, but you'll get no bonus.