In Which We Serve is a 1942 British patriotic war film directed by Noël Coward and David Lean, who made his debut as a director. It was made during the Second World War with the assistance of the Ministry of Information.

War film is a film genre concerned with warfare, typically about naval, air, or land battles, with combat scenes central to the drama. It has been strongly associated with the 20th century. The fateful nature of battle scenes means that war films often end with them. Themes explored include combat, survival and escape, camaraderie between soldiers, sacrifice, the futility and inhumanity of battle, the effects of war on society, and the moral and human issues raised by war. War films are often categorized by their milieu, such as the Korean War; the most popular subjects are the Second World War and the American Civil War. The stories told may be fiction, historical drama, or biographical. Critics have noted similarities between the Western and the war film.