India witnessed increased industrial production during the First World War due to following reasons:  

1. British industries became busy in producing and supplying war-needs. Hence, they stopped exporting British goods or clothes for colonial markets like that in India.  

2. It was a good opportunity for Indian industries to fill in empty Indian markets with their products. It was done so. Therefore, industrial production in India increased.  

3. Also the British colonial government asked Indian factories to supply the war needs like - jute bags, cloth or army uniforms, tents and leather boots, horse and mule saddle, etc.  

4. The increased demands of variety of products led to the setting up of new factories and old ones increased their production.  

5. Many new workers were employed and everyone was made to work longer hours.

Introduction:
During the First World War, industrial production in India witnessed a significant increase. This can be attributed to several factors that contributed to the growth of industries and boosted production levels.

1. Increased Demand:
- The war created a surge in demand for various goods and supplies, both domestically and internationally.
- The British Empire, of which India was a part, required a vast quantity of raw materials, food, clothing, and munitions to support the war effort.
- This increased demand stimulated industrial production in India as it became a crucial supplier of goods to the British Empire.

2. Government Support:
- The British colonial government implemented policies and provided financial support to promote industrial growth during the war.
- The Defense of India Act 1915 allowed the government to take control of industries and allocate resources as per wartime requirements.
- The government also provided subsidies, loans, and tax incentives to encourage industrialists to expand their operations and increase production.

3. Growth of War Industries:
- The war led to the establishment of new industries and the expansion of existing ones to cater to the demand for war-related goods.
- Industries such as textiles, jute, steel, engineering, and chemicals experienced significant growth during this period.
- The production of military equipment, ammunition, clothing, and other war supplies increased to meet the needs of the armed forces.

4. Expansion of Railway Network:
- The construction and expansion of the railway network in India played a crucial role in boosting industrial production.
- The railways facilitated the transportation of raw materials, finished goods, and manpower, thereby improving connectivity and reducing logistical challenges.
- This infrastructure development accelerated industrial growth and increased production capacity.

5. Migration of Workers:
- The wartime demand for labor in industries attracted a large number of workers from rural areas to urban centers.
- The migration of workers resulted in an increase in the industrial workforce, leading to higher production levels.
- The influx of labor also contributed to the growth of urban areas and the development of industrial towns and cities.

Conclusion:
The First World War created favorable conditions for industrial production in India. Increased demand, government support, growth of war industries, expansion of the railway network, and migration of workers all played a significant role in driving industrial growth during this period. This boost in production had long-lasting effects on India's industrial sector, laying the foundation for future industrialization and economic development.