In 1759, Bombay Garrison's Sepoy Companies were reorganized. In 1768 the first two regular Sepoy Battalions were formed, with a third in 1769 and a fourth in 1770. While a graduated albeit similar expansion was taking place in the other Presidencies as well, each now placed under respective Governors who subsequently rose in rank and power to become Governor Generals, by the middle of the century's Commander-in-chief was provided to the Governors for coordination of military activities. Major Stringer Lawrence filled this post with great verve. This was the first move to integrate the military assets of the three Presidencies in a coordinated manner. In 1784-85 full military powers, including the power to appoint the Commandor-in-Chief, wee retained by the board of directors, which meant the British Government. For the Governor-General, a formal Army Headquarters was created with the commander-in-chief as head. To assist him were two Principal Staff Officers, namely the Quartermaster General and the Adjutant General. By 1790 the total strength of the combined British Indian Army was 80,000. The begining of the 18th century also saw the rise of Sikhs in Punjab and the Rajputs in Rajputana. The French also established a new base of Calicut in addition to their existing bases at Surat, Pondicherry, Muslipatam, Chandernagar, Balasore and Kasim Bazar. The first invasion bu Ahmed Shah in 1774 was halted at Sirhind by a combine Mughal and Rajput force and the invaders were forced to retreat to Afghanistan.
Having well established themselves, the Europeans started increasing their influence with the princely states and often resorted to war and intrigue against them. Native soldiers were also raised by them to fight against each other and for taking sides in local wars . During the first, Carnatic war (1744-48) hostilities ensued between the British and the French. The French seized the main British base at Madras after a fierce encounter. The Nawab who had allied himself with the British, arrived near Madras with a large army. In the battle of St. Thome the French detachment of 230 European and 730 native soldiers attacked and routed a force of 10,000 of the Nawab's troops near Madras.Commanded by Dupleix, the French tried unsuccessfully for 18 months to take the British base near Madras , but had to raise the seige following the arrival of British reinforcements. In 1748 the British tried to take Pondichery, Defended by Dupleix, but were forced to withdraw. after the Treaty in Europe, they returned Madras to the British. In 1749, Ahmed Shah's second invasion was a combined raid and reconnaissance in force which led him to believe that he could conquer Punjab and Kashmir. The Dutch exploitation was finally eliminated in 1759 in the battle of Wandiwash, and Portugal's control was confined to their occupation of Goa, Daman and Diu. despite formal peace between France and Britain, hostilities between the two continued through their involvement in Indian conflicts.
During the second Carnatic War, the British, under Robert Clive with 500 soldiers and three guns , captured Arcot so as to relieve presure on a small English garrison at Trichinopally. They took advantage of native rivalries in an almost continual warfare.
The British East India Company had a remarkable organisation. It built up its own army, composed of European adventures and native troops, under English Commanders. Further military influence was exercised in 1754 by an English regular regiment, the 39 foot, at Madras, which became the backbone of the British military operations in India. Many of its officers and men were later transferred to the company's service. The French under Dupliex and its native allies, however, controlled a great part of Southern India. In Bengal, after Siraj-ud-daulah had seized Calcutta in !756, Clive recaptured it next year in January. On March 1, he took Chandenagar from the French so as clear his line of communication before pursuing Siraj-ud-Daulah. Clive found him entrenched near Plassey, north of Calcutta with 50,000 troops and 53 guns. With 1,100 Europeans and 2100 native troops, Clive launched a masterly operation and won the decisive and historic battle of Plassey. This gave the British suzerainty over Bengal,Bihar and Orissa and became lord of the vast territory.The British advanced westward along the gangetic plainand occupied areas upto Allahabad.