 Complete the following phrase:  In 1977 and 1978, Bull orchestrated the illegal sale of 30,000 155mm artillery shells, gun barrels and plans for the GC-45 howitzer as well as radar equipment to Armscor, the South African state arms corporation; with two shipments made through Antigua in 1978 and another through Spain in 1979. The South African Defence Forces arsenal of vintage howitzers  antiquated by the arms embargo  had been outperformed by BM-21 Grads during Operation Savannah in 1975. In order to counter the modern Soviet artillery deployed in neighbouring Angola, South African officials began seeking longer-ranged weapons systems and were referred to SRC. Armscor trialled the GC-45 with a new mounting to allow for increased powder loads and installed an auxiliary power unit for improving mobility in the field. The resulting G5 howitzer was vital to South African campaigns against 