Israel invades the gaza strip.

Well, according to the article it began when a Hamas commander was killed, so Gaza fired rockets into Israel kiliing 3, to which Israel responded by killing ~20 Palestinians just now, to which Gaza will respond by firing even more rockets.

I don't even want to begin describing what happened before this chain =/.

Not entirely correct, Israel had taken around 80 missiles before they finally retaliated, though most were deflected with the Iron Dome.