Final answer:
Indians volunteered to help the Allies in WW2 for a combination of securing rights and independence. India's vast economic and military contributions during the war, along with global anti-imperialist sentiment, set the stage for India's independence post-war in 1947.
Step-by-step explanation:
The motivation behind the Indian volunteers in World War II was multifaceted. Initially, participation was seen as a means to secure more rights and gain independence after the war, similar to expectations after World War I. The Great War had set a precedent, and with over 2.5 million Indian soldiers fighting in World War II, India contributed significantly to the Allied war effort. Nonetheless, the British reluctance for reform fueled the Indian nationalist movement, increasing fervor for self-rule.
During the war, the British employed over 87,000 Indians who were killed in action, heavily drawing upon India's manpower. In addition, India’s economy had become the world's fourth largest, due to its industrial growth and financial loans to Britain. This economic and military contribution spurred arguments for Indian independence. Notably, internal divisions and the Indian roles in administration and the military under British rule implied they were more than capable of self-governance.
The impact of the war weakened British power and strained its resources, undermining its ability to maintain its colonies. As the global sentiment shifted against colonialism, India's push for independence strengthened. The war’s conclusion hastened the end of the British Empire and led to India’s independence in 1947.