Self-Propelled Guns. Part-One.

Mobile Battlefield Artillery.

In someways the early development of the tank was the idea to have armoured artillery on the battlefield, but it was not until the 1930s that the United States produced the first SPG as a over armed MBT known as the Lee-Grant.

During World War-II (1939-45) Nazi-Germany became reliant more on their developments of SPG's that they had more of them than actual tanks. The idea of mobile artillery was good as long as that was their primary role, but as the war progressed Hitler in his madness and interference used them for the wrong role.

In Soviet Russia they easily became prey to the light T-34 tanks and in France and Italy to the American Sherman's. After the war Russia and America, along with many other nations saw the value of such a plat form in infantry support and even to this day they are still being developed.

U.S.A. M109 155mm, M109 105mm, SP 122, 
Russia, 2S19 152mm, 2S3 152mm.
U.K. AS90.
Sweden Bofors 155mm.
Germany Wegmann 155mm.
Japan Type 75. 

France GIAT 155mm.
Italy Palmeria 155mm. 

Israel Soltam 155mm.