The First Carnatic War (1744-48) was triggered by the War of the Austrian Succession, and saw the French win a series of victories over their English rivals in the south of India, although the pre-war situation was restored by the Treaty of Aix-le-Chapelle.
At this date the British and French were minor players on the Indian scene, and were represented by the British and French East India Companies. In the south of India the most important figure was Nizam-ul-Mulk, the Mughal governor of the Deccan (but increasingly acting as a semi-independent Nawab of Hyderabad). The southern part of his province was ruled by a subsidiary ruler, the Nawab of the Carnatic, a post held since 1743 by Anwar-ud-Din. Of the two European powers, the French had more prestige, and their governor also held the title of Nawab, giving him a place in the Mughal hierarchy. The main British possession in the area was Madras, the main French base was further south, at Pondicherry.
In general the British and French in India had ignored earlier Anglo-French wars in Europe, remaining at peace during the War of the Spanish Succession. During the War of the Austrian Succession the same happened in Bengal, but in the south the actions of British and French fleets triggered combat on land.
The fighting started in 1745 when a British squadron under Commodore Curtis Bennett arrived in the area and swept French shipping off the seas. The French Governor General, the Marquis Joseph-François Dupleix, appealed for protection from Anwar-ud-Din, and he in turn warned the British that his province was neutral territory and that no attack on French possessions would be tolerated. In response the British restricted themselves to action at sea. Dupleix also sent a message asking for help from the French fleet stationed at Mauritius under the command of Admiral de la Bourdonnais. This fleet arrived in the summer of 1746, and inflicted a minor defeat on the British (now under Commodore Edward Peyton) at the battle of Negapatam in July. Peyton retired to Ceylon to repair his fleet, leaving the French in command of the seas around Madras.
The French fleet briefly appeared off Madras at the end of August, before returning in mid-September. The resulting siege of Madras was short. The British East India Company had neglected the fortifications, and the garrison was tiny. On 21 September the British surrendered, and the French took possession of Madras.
The capture of Madras triggered a bitter argument between Dupleix and La Bourdonnais. Dupleix wanted to hand the town over to the Nawab, as compensation for breaking the Nawab's decree of neutrality, while La Bourdonnais wanted to ransom the town back to the British. This dispute dragged on into October, and eventually Anwar-ud-Din decided to intervene. He sent an army of 10,000 men under the command of his son Maphuze Khan to besiege the French in Madras. This decision backfired dramatically and led to two battles that have been seen as a major turning point in Indian history. The battle of Madras (2 November 1745) saw a French force of only 400 men rout the Nawab's cavalry, causing his son to abandon the siege. Two days later a slightly larger French army, moving to the relief of Madras, inflicted a second defeat on Maphuze Khan's army (Battle of St Thome, 4 November 1746). These two battles had the immediate effect of securing French control of Madras, while in the longer term British and French generals realised that their small armies could defeat much larger Indian forces.
The French were unable to take full advantage of their victory. The British regrouped at Fort St. David, to the south of Pondicherry. They allied with the Nawab, who provided them with a large cavalry force under the command of two of his sons. This force defeated a French army advancing towards the fort (battle of Fort St. David, 19 December 1746), but early in 1747 the French made peace with the Nawob, leaving the British vulnerable. A short-lived French siege in March 1747 ended when a British squadron arrived at Fort St. David.
Dupleix's next move was an attack on Cuddalore, a British fortified station two miles from Fort St. David. The resulting Battle of Cuddalore (27-28 June 1747) was another British victory, but was most noteworthy as the first direct clash between British and French troops in India.
Up until now the East India Company had borne the brunt of the British war effort in India, but in November 1747 a fleet of eight men-of-war, accompanied by 1,400 British regulars, left Britain. In an unusual arrangement for the British in this period, Admiral Edward Boscawen commanded both the navy and army (normally the army would provide a commander for their troops and the two senior officers would have to try and cooperate). After failing to make any progress at Mauritius, Boscawen reached the Indian coast in early August. The British now had command of the seas, and enough troops to attempt to capture Pondicherry.
The resulting siege of Pondicherry (August-October 1748) was not a great success. Boscawen wasted some time attacked an outlying fort at Ariancopang. His main batteries at Pondicherry weren't in place until the start of October, and when they finally opened fire the French counter fire was far more ferocious than the British bombardment. In mid October Boscawen decided to call off the siege.
At about the same time the Treaty of Aix-le-Chapelle (18 October 1748) ended the War of the Austrian Succession, and with it the First Carnatic War. Madras was returned to the British in return for Louisbourg in Nova Scotia and the situation briefly returned to its pre-war state. The peace in India would be short lived. In 1748 Nizam-ul-Mulk, the Mughal governor of the Deccan and semi-independent Nawab of Hyderabad died. The succession to his position was contested, and the British and French were soon dragged into the fighting between the candidates. The resulting Second Carnatic War lasted from 1749 until 1754, and saw the British strengthen their position in southern India.