The Bangladesh Navy has the third-largest fleet of countries dependent on the Bay of Bengal, including guided-missile frigates, submarines, cutters and aircraft. The Bangladesh Air Force is equipped with several Russian multi-role fighter jets. Bangladesh cooperates defensively with the United States Armed Forces, participating in the Cooperation Afloat Readiness and Training (CARAT) exercises. Ties between the Bangladeshi and the Indian military exist with high-level visits by the military chiefs of both countries. Most of Bangladesh's military equipment comes from China. In 2019, Bangladesh ratified the UN Treaty on the Prohibition of Nuclear Weapons.