"Day of Defeat is a team-based multiplayer World War II first-person shooter video game of the European Theatre of World War II. As of 2008, the game is one of the ten most played Half-Life modifications in terms of players, according to GameSpy.
Day of Defeat is a 3D multiplayer shooter that simulates squad-level infantry combat between the adversaries of World War II's European Theatre; the Allies or the Axis Powers. The goal is to complete various mission objectives.
Players can choose between the Allied armies (American and/or British armies, depending on the map) or the Axis armies. In Day of Defeat:Source there are only the American and German armies.
A round begins with two opposing teams starting simultaneously in their respective spawn area of a map. A round ends when one team accomplishes all of its objectives.
Player casualties become reinforcements which are supplied according to a timer. The reinforcements originate at spawn and can be composed of anywhere from 1 soldier to the entire team. The reinforcement timer is usually between 10-20 seconds, but this time may vary from server to server.
Like other Half-Life mods, Day of Defeat tracks each player's accomplishment in team objectives, how many enemies each player has eliminated and how many times each player has died. The game also tallies these statistics for the entire team; this reflects the team's score which is primarily based on objectives.
After many rounds, the game ends when a set time limit expires, and the team with the most objectives achieved is the winning team regardless of kills or casualties, except in the case where both teams have not achieved any objectives or are tied in the objective score. The scoreboard is displayed and the game is restarted with another map."
Source: Wikipedia, "Day_of_Defeat," available under the CC-BY-SA License.