https://www.pcgamer.com/kill-wolves-instead-of-people-in-tannenbergs-new-wolf-truce-event/

The First World War shooter Verdun celebrates the famed Christmas Truce of 1914 with a special in-game event in which players from opposing sides can get together for snowball fights, soccer games, and card exchanges. Starting today and running until April 22, something similar, yet very different is happening in the trenches of its standalone expansion Tannenberg: The Wolf Truce. 

This event, according to developer M2H, is also based on historical happenings, but from later in the war, when the carnage had driven large numbers of wolves from their normal ranges in search of food. They pushed into Germany, killing livestock and even children, and also began attacking soldiers, especially the wounded. It became such a problem that German and Russian soldiers were eventually forced to band together to fight them off.