The First World War helped in the growth of the national movement in India by creating political, economic, and social upheavals that intensified Indian discontent against British colonial rule. Key ways the war contributed to the growth of nationalism include:

• Indian participation in the war effort involved over a million soldiers and vast resources, but Indians received no meaningful political reforms in return. This widened the gap between Indian sacrifices and British promises, generating resentment.
• The war caused significant economic strain in India, including increased defense expenditures financed by war loans, high customs duties, and introduction of income tax. Inflation and crop failures led to acute food shortages and hardship for the common people, fueling anti-British sentiments.
• Forced recruitment of Indian soldiers, especially from rural areas, caused widespread anger.
• Nationalist leaders like Bal Gangadhar Tilak and Annie Besant launched the Home Rule Movement during the war, demanding self-governance. The movement gained widespread support and united various factions.
• The Lucknow Pact of 1916 between the Indian National Congress and the Muslim League symbolized Hindu-Muslim unity in the nationalist cause.
• Wartime promises such as Montagu’s 1917 statement on increasing Indian participation in government were seen as inadequate, triggering mass struggles and strengthening demands for full independence.
• The Khilafat movement mobilized Indian Muslims against British policies, and together with the Non-Cooperation Movement launched by Mahatma Gandhi, marked a new phase of mass nationalist movements.
• The brutal repression of protests like the Rowlatt Act agitation and Jallianwala Bagh massacre further alienated Indians from British rule and fueled the demand for freedom.

In summary, the First World War exposed the exploitative nature of British rule and created conditions of economic distress and political awakening that significantly strengthened the Indian national movement, setting the stage for mass movements led by Gandhi in the post-war period.