Operation Weseruebung, the German invasion of Norway during the Second World War, is considered by many military historians to be the first joint military operation involving the combined planning and execution of air, land, and sea forces. After a brief introduction and an explanation of the significance of Norway, Chapter Three will analyze the planning process and strategy used by the Germans in late 1939 and early 1940 for devising this joint operation. Chapter Four examines, primarily from an airpower perspective, the plan itself and its execution during the first day of the operation by the Germans, and the British response. Chapter Five determines how German airpower was used, and in particular, what effect the Luftwaffe attack on 9 April against the British Home Fleet had against Britain's campaign strategy to control the North Sea. The final chapter examines three important lessons United States military planners should extract from Operation Weseruebung and apply to operations in the 21st century. They are: 1) the joint operation of air, land, and sea assets produce a synergetic effect greater than the sum of their parts; 2) a difficult part of joint operations is the air command and control; and 3) airpower can decisively deny the enemy use of the land or the sea.