England French Rivalry in North America
In 1775, American Revolutionary war started in which France assisted the victory of Americans seeking independence from Britain. This was preceded with the Boston Tea Party in 1773 in America in which the natives refused to accept the British Government given monopoly of the failing East India Company over the tea sold in North America, resulted in throwing large quantities of tea overboard into the Boston Harbor. This was followed by an open war between England and France and it got its own version in India.
At home, Hyder Ali had become a French ally. The French-British hostility in Europe gave rise to the renewed hostility between the Mysore and British East India Company. Hyder Ali had become number 1 enemy of the British due to their non compliance of the terms of treaty in the previous war with Marathas.
The British too had resolved to drive the French out of India.
The local version of the French declaration of war upon England in 1778 was a raid upon the Pondicherry by the British East India Company in 1778, capturing the French outposts. In 1779, the British captured Mahe.
Mahe, the strategic port was under Hyder Ali. The capturing of the Mahe led Hyder Ali declare a war against British which is called the Second Anglo-Mysore War.