Silent Service - how do i end the war patrol?

[agathosdaimon]

I need some help - in the war patrol how do i actually end it - ie i go back to a base eg Midway, and the screen does its yellow and green flashing - but i cant find the button to end it and so what happens is htat my sub runs out of fuel and i lose. When i am back at base, what button do i push to officially end the patrol?

i am referring specifically to the dos version, the version which is on steam