midnight on the
31st of December
`` But will that be possible , field-marshal ? Can all our troops be prepared at so short a notice ? '' `` That is your task , Gneisenau ; ideas are your province , execution is mine . You are my head , I am your arm ; and these two , I believe , ought jointly to enable us to cross the Rhine at midnight on the 31st of December , as the holy army of vengeance , which God Himself sends to Bonaparte as a New-Year 's gift . But come , Gneisenau , let us ride to the ball . I must dance ! Joy is in my legs , and I must allow it to get out of them .