At the time of World War I, it was known as the British Indian Army or British Indian troops. The Indian troops were deployed in war without preparation and without proper clothing in a foreign land, in winters. Yet they played an important role as part of the allied forces and their performance in battle was remarkable and praised by all countries.
Over 1.5 million soldiers from various parts of India including Punjab, Maharashtra, Uttar Pradesh, Bihar and Tamil Nadu volunteered to take part in Britain's war effort. They fought both in the Western Front and in the Eastern theatre of war and continued even beyond 1918 in Afghanistan & Persia (up to 1920). The gallant Indian soldiers earned various medals and honors for their services. These include: 11 Victoria Cross, 5 Military Cross, 973 Indian Order Of Merit & 3130 Indian Distinguished Service Medals during the WW I.
As far as the number of regiments that took part in the war is concerned about 12 Cavalry Regiments, 13 Infantry Regiments & several other units of other Arms / Services participated in the 13 Campaigns of WW 1. India was fighting on the British side and the only satisfaction that Indians could have was that the war served as 'training ground for fighting in a modern warfare'.
In 1914, at the outset of the war, the strength of the British Indian army was 23,000 British and 78,000 Indian soldiers. India sent the following contingents to various theatres at the outset of war:
India provided Britain with not just men and material, but finances as well to fight World War 1. India gave £100 million towards the cost of the war. An initial offer of a lump sum of £100 million was made in 1917. Three quarters of this amount was raised through War loans or bonds and the rest given by the Government of India.
In terms of direct monetary contribution India gave £146.2 million from its revenues. According to one account, there were approximately 172,815 animals, which included 85,953 horses, 65,398 ponies and mules, 10,781 camels, 5,061 bullocks, 5,692 dairy cattle and 369.1 million tons of supplies and stores, which left the ports of India for various destinations.
Within the first few weeks of the war, India supplied 70,000,000 rounds of small arms ammunition, 6,00,002 rifles, mortars and machine guns. Considerable quantities of shell cases were manufactured. The Army Clothing Department produced 41,920,223 garments between 1914 and 1918. Raw materials like rough tanned hides; wool, manganese, mica, salt, timber, bamboo, raw silk, hemp, coir, tea, rubber, petroleum oils and foodstuffs were supplied.
A total of 2,737,862 tons of items such as rice, flour, atta, ghee, sugar, tea, tinned meat, grain and hay for animals, jam, biscuits and firewood were shipped from India up to March 1919. You can see the huge effort that is required to maintain troops in war. More importantly, India had all these even in those times and could proudly give to the countries that needed them.