Due to time and resource constraints, the German invasion of Norway was planned using a tourist map!

Nikolaus von Falkenhorst was a German General in World War II. Falkenhorst came from an ancient Silesian military and noble family. On February 20, 1940, Hitler approached Falkenhorst and informed him that he’d be the ground commander for the invasion of Norway.

He gave Falkenhorst until 5 p.m. the same day to come up with a basic plan. Without any real time or resources to use, he grabbed a Baedeker tourist guide at a stationary store on his way to his hotel. In his room he came up with a basic plan using maps found in the tourist guide.

Hitler approved of the plan and Operation Weserubung was set in motion. Falkenhorst’s Operation was a success. The German Navy suffered heavy losses. The Allied forces tried to counter the German’s move, but Falkenhorst’s troops eventually drove them out.

Falkenhorst remained in Norway after the invasion as commander of the German troops from 1940 to 1944. He ordered his troops to treat the Norwegians with courtesy, though.

(Source)