He joined the army in 1903 and served in World War I in regimental and staff roles, including a stint in Finland.

On 20 February 1940, Hitler informed Falkenhorst that he would be ground commander for the invasion of Norway Operation Weserübung, and gave him until 5 p.m. the same day to come up with a basic plan.

In December 1942, Falkenhorst made a plan for the invasion of Sweden if necessary (Operation Polarfuchs; "Arctic Fox") [citation needed] which required 10 German divisions.

[3] He distributed the order in 1942, then reminded his subordinates about it in 1943, insisting that the captured commandos be handed over to the SD, the intelligence service of the SS, for execution.

Hedin said Falkenhorst deserved mercy since he had successfully lobbied Hitler to spare the lives of 10 Norwegian resistance members who had been condemned to death for sabotage.

In 1968, following a heart attack, he died at Holzminden, West Germany, where his family had settled after fleeing from Lower Silesia.