The protectorate was claimed to extend from Cape Honduras in the north to the mouth of the San Juan River in the south, including San Juan del Norte. Nicaragua protested again and sent forces to San Juan del Norte, which the Miskito King George Augustus Frederic II replied to with an ultimatum demanding all Nicaraguan forces to leave before January 1, 1848. Nicaragua appealed to the United States, but the Americans, then at war with Mexico, did not answer. After the ultimatum expired, Miskito-British forces led by the King and Patrick Walker, and backed by two British warships, seized San Juan del Norte. They also destroyed Serapaqui, where the British prisoners captured during the first attempt on San Juan del Norte were interned, and advanced to Lake Nicaragua, during which Walker drowned. On March 7 Nicaragua signed a peace treaty where it ceded San Juan del Norte to the Mosquito Kingdom, who renamed it Greytown after Charles Edward Grey, governor of Jamaica.