Tonight - it'll be exactly 75 years since the 133 air crew led by Wing Commander Guy Gibson - set off from RAF Scampton to strike at Germany's industrial heartland.
Its been called one of the 'most daring raids in history'.
Their targets were the dams on the Sorpe, Edersee and Mohne rivers.
The attack required a new type of bomb, specially designed by engineer Barnes Wallis.
It would bounce across the surface of the water, hit the dam and then explode, hopefully punching a hole in the structure.
On the night 617 was divided into 3 flights, each attacking one dam.
The Mohne and the Eder were successfully breached the Sorpe was not.
The raid came at great cost 53 allied aircrew were killed, with 8 of the 19 Lancasters begIn shot down.
It also has a controversial legacy.
Hundreds of civilians were killed in the flooding that followed the dams being breached - However, it may have indirectly helped shorten the war:
The mission's since been immortalised - most famously in the 1955 film.