The Rhine was the last major natural obstacle before the German heartland. Forcing the crossing of a large river against an opponent with intact forces and prepared defenses was understood to be one of the most difficult military operations, with historical precedents stretching back through European history. The American Army was going to have to cross the Rhine somewhere along its length in the Ninth Army sector, and the Germans knew it. The question was where, with what forces, and with what level of defending concentration to meet them.
Operation Viersen in this context was the culmination of the entire Ghost Army’s operational development. All the previous operations — the experiments in Normandy, the operations in France and Belgium, the deceptions that had supported the conventional advance — had led to this moment: the opportunity to shape German understanding of one of the most consequential events of the war’s final phase.
## The River Crossing in Military History
River crossings have been among the most studied and feared of military operations throughout recorded history.
The fundamental problem is that a river creates a natural barrier that concentrates the crossing force in a specific location, eliminates the ability to maneuver freely, and creates a window of maximum vulnerability while troops are in transit. An opponent who knows where the crossing will occur can concentrate forces to destroy the crossing element while it is at its most exposed — in boats, on pontoon bridges, or in the water itself.
Historical commanders have understood for centuries that successful river crossings require either overwhelming force, surprise about the crossing location, or both. The American operations in March 1945 aimed for both: the Army had the strength to force crossings at multiple points, and the deception operations aimed to ensure that the specific crossing points were not defended at maximum concentration when the operation began.