In The Hunger Games: Mockingjay - Part 1 (2014), they never explained why the capital bombed them originally. Why did the capital bomb district 13 before the movie started?
"I was always told there was nothing left of 13."
and
"The capital bombed the surface to rubble, but we're military so we learned to survive down here."
It was destroyed during the First Rebellion when the united districts of Panem rebelled against the Capitol's oppressive rule.
Near the end of the war, District 13 trained nuclear missiles on the Capitol, hoping to destroy the Capitol even if the result was mutually assured destruction. However, District 13 set up a secret deal with the Capitol - they would withdraw their forces from the war and present the illusion that Capitol bombers equipped with Toxic bombs destroyed District 13. 13 withdrew and rebuilt their district underground. The Capitol's bombers then destroyed the district on the surface. Without 13's aid, the remaining rebel forces were put down by the Capitol.
The Hunger Games commemorate the Capitol's victory in this war and serve to remind the citizens of Panem of the futility of rebellion.
