the falklands war was excepted............
Romanian declaration of war in ww1 was IMHO suprising.
Don't now if this even counts, but... Operation Barbarossa.
Nazi Germany's invasion of the Soviet Union caught Stalin totally by surprise.
Iraq invading Kuwait was pretty unexpected right? Even for someone as unstable as Saddam?
Not at all. Sure people werent counting down to it, but it looked possible for weeks beforehand
You mean El Salvador and Honduras? Meh. They were at each other's throats for quite a while. The football game in question was just a pawn of the fray and not really a causing factor.