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It was a series of widespread unofficial ceasefires along the Western Front of the First World War around Christmas 1914.
Christmas truce
The Christmas truce (; ) was a series of widespread unofficial ceasefires along the Western Front of the First World War around Christmas 1914.

who was involved in the ww1 christmas truce British and German troops
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Christmas truce [SEP] Introduction
There were joint burial ceremonies and prisoner swaps, while several meetings ended in carol-singing. Men played games of football with one another, creating one of the most memorable images of the truce. Hostilities continued in some sectors, while in others the sides settled on little more than arrangements to recover bodies. The following year, a few units arranged ceasefires but the truces were not nearly as widespread as in 1914; this was, in part, due to strongly worded orders from the high commands of both sides, prohibiting truces. Soldiers were no longer amenable to truce by 1916. The war had become increasingly bitter after heavy human losses suffered during the battles of 1915.