midnight
Napoleon 's spies at Frankfort and on the Rhine heard only the grumbling of Blucher , but they did not see the preparations of Gneisenau . On the 26th of December orders were dispatched to the commanders of the different corps of the great Silesian army , communicating the time and place of crossing the Rhine , and on the 31st every soldier of that army stood on the bank ready for the passage . This was to be effected at three different points -- Mannheim , Caub , and Coblentz . The grand , all-important moment had come ; midnight was at hand . It was a clear and beautiful night ; the deep-blue sky was spangled with stars , and the air cold and bracing . None saw the blank columns moving toward the Rhine . The French , on the opposite side , were asleep ; they did not perceive Field-Marshal Blucher , who , at Caub , on the bank of the river , was halting on horse back by the side of his faithful Gneisenau , apparently listening in breathless suspense .