The medium artillery caterpillar at-s was developed over forty years, and entered service in the soviet army in the early fifties, but was replaced by the medium artillery crawler tractor ats-59. Besides its use in the soviet army, the at-s was used by all the countries of the former. Warsaw pact, with the exception of czechoslovakia, and was exported to countries like china, egypt, finland, syria and yugoslavia. At-s can carry a maximum payload of 3000 kg towing trailers or weapons whose weight is 16 000 kg. Conventional weapons include ks-19 anti-aircraft guns to 100 mm howitzers and 152 mm.