The other day, our military was following a few insurgents from Afghanistan and being the slightly over-zealous sorts, they "accidentally" dropped a bomb on the heads of Pakistani soldiers, killing 11 of them. Now Pakistan's making a big stink, claiming we "aren't allowed to invade their country, even if we're following insurgents without getting their OK," lots of ridiculous fist shaking, and so our government and military decided to send them a few cards, just to let them know how sorry we are.

"US Defends Airstrikes That Pakistan Says Killed 11 Soldiers"- AP
"Footage of deadly US air strike" - BBC News