Dennis Showalter is Professor of History at Colorado College, Past President of the Society for Military History, and the Editor in Chief of Oxford Bibliographies in Military History. Joint Editor of War in History, he specializes in comparative military history and the military history of modern Germany. His recent monographs include The Wars of German Unification, Patton and Rommel: Men of War in the Twentieth Century, and Hitler’s Panzers.

April 1940 witnessed the first, arguably the most economical, and one of the broadest-gauged combined-arms operations in modern military history. The Norwegian campaign is usually considered in the contexts of its end-game and its set-pieces: the drawn-out fighting around Narvik, the Royal Navy’s annihilation of a German task force. Neglected in that context is an initial German invasion plan that was daring in its conception, economical in its use of force, and almost successful in paralyzing an entire country in a matter of a few days.

Norway had deliberately neglected its armed forces in favor of social welfare problems at home and “soft power” internationally. Nevertheless, Nazi Germany was willing enough to leave Norway alone. As a neutral state, Norway transshipped Swedish iron ore vital to the German war effort through the northern port of Narvik. But by the spring of 1940, British pressure on these shipments had reached a point where a preemptive strike by Germany seemed a reasonable strategic move.

The navy took the lead in planning. It was the weakest of Germany’s armed forces — certainly no match in numbers for the Royal Navy. The army and the air force were primarily concerned with planning for the “real war:” the attack on the Western front projected for the coming summer. Few Luftwaffe Stukas, fewer army panzers, could be spared for a secondary campaign. Finesse must compensate for mass. An invasion mounted on a shoestring could not afford what Clausewitz calls fog and friction. Tactically, success depended on surprise. Surprise depended on timing and coordination, and those in turn required expanding the invasion’s scope exponentially.....