The Rochev and Doher Self-Propelled Guns (SPG) used by the Israel Defense Forces (IDF) are the Israeli versions of the US made M109, M109A1 and M109A2 known artillery pieces. The first M109 arrived to the IDF in the early 70s as a new and modern Self Propelled system, compared to other 155 mm mobile artillery that were in use, as towed guns or installed on the old Serman tank chassis. Many conversions were done by the IDF on M109 derivatives in order to fit them for the doctrine and requirements of the IDF Artillery Corps. The IDF is one of the largest users of the M109 excluding the United States of America.