Industrial production in India increased during the First World War due to the following reasons

1. The British mills were busy with war production to meet the needs of the army; thus, Manchester imports into India declined.
2. With the decline of imports suddenly, Indian mills had a vast home market to supply.
3. As the war prolonged, Indian factories were called upon to supply war needs also, such as Jute bags, cloth for uniforms of soldiers, tents, leather boots.
4. New factories were set up, and old ones organised multiple shifts; during the war years, Indian industries boomed.
5. Overall, the First World War gave a boost to Indian industries.