The planning and execution of Operation Weserübung was the first major joint operation of its kind in history utilizing naval, ground, air, and airborne forces. Its conduct proves to be one of the most noteworthy applications of operational art and the principles of war during all of World War II. The principles of surprise and security were the most critical in the German success. The German planning taking into account and exploiting the operational factors of time, space and force are another key element in why this operation is worthy of further analysis and study. Additionally, the operational lessons learned that could be applied from the belligerents' experiences further illustrate several important lessons that can apply today. From the Germans we saw the importance of planning around apparent disadvantages, command and control as it relates to operational objectives and commanders intent, and the importance of initiative in military operations. From the British, the pitfalls of mirror imaging and a lack of decisiveness can prove fatal in military operations. Lastly, from the Norwegian side we see the importance of national defense for maintaining a nations' own self-determination against outside belligerents.