Franklin D. Roosevelt started the development of a nuclear weapon.
As an active military leader , Roosevelt implemented a war strategy on two fronts that ended in the defeat of the Axis Powers , and he initiated the development of the world 's first atomic bomb .	Axis Powers	Axis Powers	atomic bomb	nuclear bomb
The first test of a fission -LRB- `` atomic '' -RRB- bomb released the same amount of energy as approximately 20,000 tonTNT .	fission	nuclear fission	first test	Trinity (nuclear test)	test	Ivy Mike
A nuclear weapon is an explosive device that derives its destructive force from nuclear reactions , either fission -LRB- fission bomb -RRB- or a combination of fission and fusion -LRB- thermonuclear weapon -RRB- .	fission	nuclear fission	fission bomb	fission bomb	fusion	nuclear fusion	thermonuclear weapon	thermonuclear weapon
