Many of the dramatic war films in the early 1940s in the United States were designed to create consensus at the expense of "the enemy." In fact, one of the conventions of the genre that developed during the period was that of a cross-section of the United States which comes together as a crack unit for the good of the country.
War films (like films in any genre) tend to have a number of cliches associated with them: for instance, in many 1940s and 1950s war film, a small group of men will tend to be fairly diverse ethnically, but most of the characters will not be developed much beyond their ethnicity; the officer immediately ranking the main character will tend to be both unreasonable and unyielding; almost anyone sharing personal information--especially plans for after returning home--will die shortly after sharing the plans; and anyone acting in a cowardly or unpatriotic manner will either convert to heroism or die.
However, other films are quasi-documentary in nature, and reflect what the screenwriters feel were the thoughts, words, and actions of the participants in a battle. The American Civil War film Gettysburg was based on actual events during the battle, including the defense of Little Round Top by Colonel Joshua Chamberlain.
Many war films have been produced with the cooperation of a nation's military forces. The United States Navy has been very cooperative since World War II in providing ships and technical guidance. However, this strategy can backfire. The German Ministry of Propaganda, in making the epic war film Königsburg in January 1945, used several divisions of soldiers as extras. Propaganda Minister Joseph Goebbels believed the impact of the film would offset the tactical disadvantages of the missing soldiers.
If they do not cooperate, then another country's military may assist. Many 1950s and 1960s war movies, and the Oscar-winning film Patton were shot in Spain, which had large supplies of both Allied and Axis equipment. The Napoleonic epic Waterloo was shot in the Ukraine, using Soviet soldiers (and incidentally, helped scholars learn why Napoleon preferred the tactics in attacking in column). Saving Private Ryan was shot with the cooperation of the Irish army.
Notable War Films
French and Indian War
American Revolutionary War
Napoleonic Empire Wars
Texas War of Independence
American Civil War
World War I
Spanish Civil War
World War II
Algerian War of Independence