The T-90 is a Russian third-generation main battle tank that is essentially a modernisation of the T-72B, incorporating many features of the T-80U (it was originally to be called the T-72BU, later renamed to T-90). It is currently the most modern tank in service with the Russian Ground Forces and Naval Infantry. Although a development of the T-72, the T-90 uses a 125mm 2A46 smoothbore tank gun, 1G46 gunner sights, a new engine, and thermal sights.