Not from a 'film' as such, but the 3 part docudrama about Dunkirk, written by Alex Holmes in 2004.
Away from the action, Capt Bill Tennant, RN HQ Dunkirk, discusses the desperate evacuation to Major-General Harold Alexander:
"If they break through tomorrow, I suppose we'll have to capitulate. How does one capitulate?" Tenant grimly asks Alexander. "I don't know. It something I've never been asked to do", Alexander replies.
You really need to watch this pic to feel the impact.