You will be home before the leaves have fallen from the trees. So said Kaiser Wilhelm II to his German army in August 1914. But World War I would rage for more than 4 years, taking the lives of nearly 10 million soldiers. Some of the most unrelenting combat was waged along the infamous Western Front, where, for one unforgettable Christmas in 1914, enemies set guns aside and came together in friendship. And the Soldiers Sang, written by J. Patrick...