The First World War was the first conflict to make extensive use of CAS, albeit using relatively primitive methods in contrast to later warfare. Even so, it was clear that coordination between aerial and ground forces via radio communication typically made such attacks more effective. Appropriately modified, the British F.E 2b fighter became the first ground-attack aircraft, while Germany produced the first purpose built ground attack aircraft in the form of the Junkers J.I; the Sopwith Camel was another successful early platform. Both the Sinai and Palestine Campaign and the Spring Offensive of 1918 made extensive use of CAS aircraft. The interwar period saw CAS doctrine continue to advance, although theorists and aviators would often clash over its strategic value. Several different conflicts, including the Russo-Polish War, the Spanish Civil War, colonial wars in the Middle East and the Gran Chaco War, were noticeably impacted by CAS operations.