system lacked the ability to shoot down aircraft flying at high altitude. After some discussion it was agreed to supply the PAVN with the S-75. The decision was not made lightly, because it greatly increased the chances that one would fall into US hands for study. Site preparation started early in the year, and the US detected the program almost immediately on 5 April 1965. On 24 July 1965, a USAF F-4C aircraft was shot down by an S-75. Three days later, the US responded with Operation Iron Hand to attack the other sites before they could become operational. Most of the S-75 were deployed around the Hanoi-Haiphong area and were off-limits to attack (as were local airfields) for political reasons. On 8 September 1965, during the 1965 Indo-Pak war, an Indian S-75 Dvina was fired at an unidentified target believed to have been on a night mission above Ghaziabad near Delhi during the height of a paratrooper scare. Subsequent news reports would claim the destruction of a Pakistani C-130 west of Delhi, showing a photograph of the wreckage of the self-destructed missile as evidence of airplane wreckage. According to Indian sources, no Pakistani aircraft penetrated so deeply into Indian territory. The missile system was used widely throughout the world, especially in the Middle East, where Egypt and Syria used them to defend against the Israeli Air Force, with the air defence net accounting for the majority of the downed Israeli aircraft. The last success seems to have occurred during the War in Abkhazia (1992–1993), when Georgian missiles shot down a Russian Sukhoi Su-27 fighter near Gudauta on March 19, 1993. During the siege of Bihac, in the Bosnian War (1992-1995), Serb forces from Krajina fired at least three S-75 in the ground-to-ground mode at the Bosnian city of Cazin. In the Yemeni Civil War (2015-present), Houthis modified some of their S-75 into surface-to-surface ballistic missiles to attack Saudi bases with them. War in Vietnam: Countermeasures and counter-countermeasures Between 1964 and early 1965 the Vietnamese had nothing to threaten American pilots in the air. U.S aircraft flew at an altitude of 4−5 kilometers, and the Vietnamese anti-aircraft guns were unable to reach them. However, after an S-75 shot down a U.S. F-4 Phantom aircraft, the U.S. bombers began to descend below three kilometers, below the minimum operational height of the Dvina. This brought them within the reach of Vietnamese anti-aircraft