Okay, what exactly happened there?
I destroyed their tank. Killed a bunch of their dudes, captured 3/4 trenches, lost my tank, lost two squads of men, halfway to the last trench with four squads of riflemen on the way, they have NO units on the field, and my bitches SURRENDER?
Here's the easiest way to gain speed:
Go sideways, and jump as low as possible to get as many "nice entry" bonuses as possible to gain speed. Do this for 1 min 50 secs, and with the last 10 jump as straight up as you possibly can.
This works for the Hard and Impossible badges.
Keep this comment alive if it works!