Languages in film: an overview

In films that have people speaking different languages in the story, there are some different ways it's handled on screen.  Here are all of the ways it's been handled that I can think of:

• Authentic: Both sides speak the language they would actually be speaking in real life.  Examples include: Stalingrad, The Longest Day, The Battle of Britain, A Bridge Too Far, Downfall, and Tora Tora Tora.
• One side speaks English, the other side speaks its own language: In reality neither side would be speaking English, but in the film one side does.  Examples include Cross of Iron (Germans speak English while Soviets speak Russian), The Pianist (Poles speak English, Germans speak German), and The Beast (AKA The Beast of War: Soviets speak English while Afghans speak Pashto)
• Both sides speak English: examples include The Train, The Blue Max, and Enemy at the Gates.
• Accent equals language: Used in the long-running Britcom 'Allo 'Allo; everybody speaks English on the show, but whatever accent they're using signifies which language they're speaking.  In Gorky Park, British-accented English stands in for Russian (more specifically, characters speaking Russian as their native language), while American-accented English represents American characters speaking fluent Russian, albeit with a heavy American accent.  In The Fourth Protocol, it's reversed; American-accented English represents Russian, while British-accented English represents English.
• Switch to English: The film starts with characters speaking another language, but after a few lines they start speaking English (while implying that they're still speaking the other language).  Examples include The Hunt For Red October and Valkyrie.  In The Hunt For Red October, the Soviet characters switch from Russian to English, then back to Russian when they encounter Americans.
• Other: Sometimes films have a language situation that doesn't fit into the above categories.  For example, in Reunion, a Jewish boy growing up in Nazi Germany eventually flees to America, returning to Germany four decades later.  While he's growing up there, everyone speaks English, but when he returns, everybody speaks German, which he now only speaks haltingly; this shift represents his loss of proficiency in his original language after decades of speaking another language.  In The Odessa File, English is spoken throughout in scenes taking place in the "present" (except for the song Schwarzbraun ist die Haselnuss), but unsubtitled German is spoken in flashback sequences.

Sometimes (like in The Blue Max*) songs get translated, while other times they don't, so in Valkyrie and Cross of Iron the German characters speak English but still sing in German and in The Beast the English-speaking Soviet tank crew plays a Russian language song** on the radio.

*A translated version of Das Polenmädchen
**The song "Trolleybus" from the band Kino