In October 1986, Iraqi aircraft began to attack civilian passenger trains and aircraft on Iranian soil, including an Iran Air Boeing 737 unloading passengers at Shiraz International Airport. In retaliation for the Iranian Operation Karbala 5, Iraq attacked 65 cities in 226 sorties over 42 days, bombing civilian neighbourhoods. Eight Iranian cities came under attack from Iraqi missiles. The bombings killed 65 children in an elementary school in Borujerd. The Iranians responded with Scud missile attacks on Baghdad and struck a primary school there. These events became known as the "War of the Cities". The "War of the Cities" resumed and peaked in 1988, when Iraq dropped 40 tons of high explosives on Tehran using modified Scud missiles (dubbed "al-Hussein" missiles) over seven weeks, causing panic among civilians and prompting almost 1 million residents of Tehran to temporarily flee their homes. Nevertheless, scholars have noted that this still "ranks as one of the smallest strategic bombing campaigns in history," paling in comparison to strategic bombing during World War II, which saw 1.2 million tons of bombs dropped on German cities in 1944 alone, or more recent events such as the so-called "Christmas bombings" of North Vietnam, which saw 20,000 tons of bombs dropped on Hanoi and Haiphong in a mere eleven days. In total, 10,000–11,000 civilians died as a result of the aerial bombardment of Iranian cities with the majority of those deaths occurring in the final year of the war.