Ironically, it was the generals who proposed the truce. Both sides recognised the need to clear no man's land of rotting corpses, and this I suspect is what the majority of ordinary soldiers spent the day doing. The gift-swapping may also have been the idea of the officer class. It has to be remembered that in 1914 the armies were made up of regular troops and volunteers; they were unlikely to have fraternised with the enemy unless their superiors had encouraged them to do so. Clearly someone high up decided that it was all getting out of hand. Backsides had to be covered, so the firing began again. In many places it had never stopped.