During the First Congo War, the Angolan government joined the coalition to overthrow Mobutu's government due to his support for UNITA. Mobutu's government fell to the opposition coalition on 16 May 1997. The Angolan government chose to act primarily through Katangese gendarmes called the Tigres, which were proxy groups formed from the descendants of police units who had been exiled from Zaire and thus were fighting for a return to their homeland. Luanda did also deploy regular troops. In early October 1997, Angola invaded the Republic of the Congo during its civil war, and helped Sassou Nguesso's rebels overthrow the government of Pascal Lissouba. Lissouba's government had allowed UNITA the use of cities in the Republic of Congo in order to circumvent sanctions. Between 11–12 October 1997, Angolan air force fighter jets conducted a number of air strikes on government positions within Brazzaville. On 16 October 1997 rebel militia supported by tanks and a force of 1,000 Angolan troops cemented their control of Brazzaville forcing Lisouba to flee. Angolan troops remained in the country fighting militia forces loyal to Lissouba engaged in a guerrilla war against the new government.