Okay, who's the good guy and who's the bad guy?
To Texans, the Mexicans were the bad guys at the Alamo. To the Santa Ana , the Texicans defying the law with their insistence on bringing slavery to town.
To most Americans, the English were the bad guys during our revolution , but King George saw the colonials as rebels and traitors to the crown.
At the Little Big Horn, most of us were taught that Custer was the good guy fighting the willful and recalcitrant Indians. To Sitting Bull and Crazy Horse, Long Hair Custer was a murderer representing a people stealing their ancestral lands and destroying their way of life.
Through most European history from the middle ages on, the bad guy was bad only until his child was marriage fodder for an alliance beneficial to both sides.
We have come to despise the idea of a sneak attack. But really, aren't all military attacks secret until launched? Imagine this phone call: "Herr H, General Ike is on the phone. He'd like you to know his forces will be landing in Normandy starting about about dawn of 6 June...weather permitting, of course. Gen. Monty will be there as well and they said they didn't want to surprise you."