The 2S7 is a late Cold War era self-propelled howitzer of Russian origin. In 1967 a requirement for a large caliber long range self-propelled howitzer was issued and in 1976 the first 2S7 were in active service. The 2S7 has the nickname Pion, which is peony in English. The 2S7 Pion is the most powerful mass produced self-propelled howitzer in existence.

The 2S7 is based on a highly modified and stretched T-80 chassis. Four crewmembers are seated in the front cabin, the engine is mounted behind it and three crew members are in the rear compartment. The ordnance is mounted at the rear. A giant spade at the rear is lowered to provide stability while firing.

The 2S7 is fitted with the massive 56-caliber 203mm 2A44 howitzer. With standard ammunition it has a range of 37.4 km and a rocket-assisted projectile can be fired out to 47.5 km. The rate of fire is 1.5 rounds per minute. Four rounds of ammunition are carried on the 2S7 with the remainder on a support vehicle. The improved 2S7M carries 8 rounds and has a rate of fire of 2.5 rpm. No secondary armament is fitted.

The steel armor protects the crew against small arms fire and shell splinters when on the move. In the firing position the crew members are exposed since the ordnance is mounted in the open. An NBC system is fitted, but smoke grenade launchers are not.

The 2S7 is based on a tracked chassis that provides a reasonably good cross country performance given its size and weight. The 780 hp V-46 diesel engine provides propulsion. Even with this amount of power the 2S7 remains a quite slow vehicle. The improved 2S7M uses the more reliable 840 hp V-84 diesel engine.

The 2S7 Pion was used by many USSR nations. It is estimated that over 1.000 units have been built. Today the 2S7 is relatively uncommon as with the end of the Cold War the need for such a powerful weapon system has faded.