 Complete the following phrase:  ZSU-23-4 units saw active service in the Yom Kippur War 1973 and other Arab-Israeli conflicts, the IranIraq War 19801988, and the First Gulf War 1990. During the 1973 Yom Kippur War, the system was particularly effective against the Israeli Air Force. Israeli pilots attempting to fly low in order to avoid SA-6 missiles were often shot down by ZSU-23-4s as in Operation Doogman 5. During the SovietAfghan War ZSU-23-4 units were used widely and to great effect against mujahideen positions in the mountains, the ZSU-23-4s guns being able to elevate much higher than the weapons on BMPs, BTRs, T-55s, or T-62s. They were also used to suppress defensive positions around the presidential palace during the initial 