In 1828, the Mexican government sent General Manuel de Mier y Terán on a mission to determine the United States-Mexico boundaries between the Red and Sabine rivers. Mier y Terán’s mission also included studying the number of Anglo-American settlers in Texas and determining the attitudes of those living in Texas.
it wasn't the British who declared war the colonists started protesting and eventually the colonists started a revolution because king George the third wasn't treating them fairly.