In August 1976, North Korean soldiers attacked a group of US and South Korean men trimming a poplar tree in the heavily-guarded zone that divides the two Koreas.
Two US officers were bludgeoned to death with axes and clubs.
After three days of deliberations going all the way up to the White House, the US decided to respond with a colossal show of force.
Hundreds of men - backed by helicopters, B52 bombers and an aircraft carrier task force - were mobilised to cut back the poplar.
Six of the men who took part told the BBC about their part in the most dramatic gardening job in history.