The Proton launch vehicle was developed in the 1960's as a two stage intercontinental ballistic missile capable of lofting the heaviest warheads in Russia's arsenal.  The heavy lift capability of the Proton was appealing to the leaders of Russia's space program as they prepared to compete against the US in the race to the moon.  The Proton was the second of three vehicle's developed in this effort.  The smallest being the Soyuz and the largest being the N-1.  By adding a third stage and combining the three stage vehicle with the Block-D LOX / kerosene upper stage, the Russian space agency could place large manned payload on trans-lunar trajectories.  Today, the Proton is the heavy lift work horse of the Russian launch vehicle fleet.  Capable of delivering 46,000 lb to LEO, the Proton will be a crucial asset in deploying the International Space Station.  In 1997, Lockheed Martin signed an agreement with Russia to market the Proton Internationally as part of their International Launch Services subsidiary.

The Proton is a three stage storable propellant launch vehicle.  For higher altitude missions requiring a fourth stage, the Block-DM has been used.  Over the past several years, the Russian's have been developing the Breeze-M, a larger version of the Breeze-K currently employed as the Eurockot third stage.  The Breeze-M will allow the Proton to increase its GTO payload capability by 25% to 12,125 lb.  The first Proton M flew in April 2001.