Dominator invasion

The Dominator Invasion was the hostile attack on Earth-1 by the alien race known as the Dominators who had the goal of wiping out the planets meta-human populace along with the rest of all life on earth. However the various heroes of Earth-1 along with help from the Alien super hero Supergirl who hailed from the alternate earth of Earth-38 managed to repel the Dominators.

Background
In the year 1951 on Earth-1, the Dominators landed on Earth, abducting humans to gather information about them. After President Ike Eisenhower waited for too long without action, the extraterrestrials attacked, killing hundreds of soldiers and capturing more. This was due to the emergence of the meta human super hero team The Justice Society of America. After this they simply left.