Answer
The Allied military mission in Siberia was involved in the betrayal of Alexander Kolchak. The mission was led by General William Graves, who was tasked with helping Kolchak's forces fight the Bolsheviks. However, Graves was reluctant to support Kolchak's regime, and he eventually withdrew his support. This led to the collapse of Kolchak's forces and his eventual execution by the Bolsheviks.