Their armies launched a joint surprise attack on the Jewish Yom Kippur holiday (the most sacred Jewish day of all in which each Jew must atone for his sins, pray and avoid eating and drinking) – the Syrian forces attacking fortifications in the Golan Heights and the Egyptian forces attacking fortifications around the Suez Canal and on the Sinai Peninsula. The troops inflicted heavy casualties on the Israeli army. After three weeks of fighting, though, and with U.S. air-lifted reinforcements of weapons and equipment (first shipment arrived on 9 October 1973), the IDF pushed the Syrian forces beyond the original lines.