Break immediately, co-operate from the start. I don't care for my country enough to actually get tortured, die, sure, but tortured, no way, man.

Then try to feed them as much misinformation as possible, while keeping to the truth. So, for D-Day, give them the correct date, but put it a hundred kilometers to the left of the actual location. Give them them sligtly incorrect plans, tell them of other operations planned that will force them to split troops (such as, say, hinting at an amphibious invasion of the Balkans and paratrooper landings in the Netherlands).