War sees the Axis and Allies fighting each other on a big map with multiple unique objectives. In the demo at E3, the Axis side must defend several objectives while the Allies rush them and attempt to make advances and push the Axis side back. Their ultimate goal is to reach the other side of the map and destroy the anti-air guns destroying the planes that are carrying soldiers and other reinforcements. The mode promotes heavy amounts of teamwork so the teams can defend/take the objectives.
In the two gameplay videos below, you'll see just how intense the modes can get and how using various weapons, tactics, and teamwork will help you succeed in War. The first video features no commentary (aside from the first minute and 15 seconds, the video starts at the 1:15 timestamp) and shows raw gameplay of the Allies side. The second video features both sides and features commentary and even communication with one of the player's colleagues.
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