Answer:
WWII
Step-by-step explanation:
Great Britain granted independence to most of its empire by the end of WWII. By the beginning of the 20th century, other great powers had arisen, such as the United States and Germany. As WWI began, Great Britain relied heavily on its colonies, and the fighting took a heavy toll on the military and financial resources of the empire. By the end of WWI, the empire was at its largest, but severely weakened.
During WWII, some of Britain's colonies were occupied. Moreover, the role of Great Britain in the war, despite its victory, weakened its image abroad, and the loss of prestige accelerated its decline, leading to independence movements in many of its colonies.