On June 13th, 1917: The deadliest German air raid on London during World War I.
A formation of German Gotha G.IV heavy bombers (part of Kagohl 3, the "England Squadron") carried out the first major daylight raid by aircraft on the British capital. Around 20 Gothas took off from bases in occupied Belgium; 14–18 reached the London area after some turned back due to mechanical issues. Flying at around 8,000–12,000 feet in clear daylight conditions, they faced minimal effective opposition from British air defences or fighters, which struggled to reach altitude in time.
Bombs began falling around 11:25–11:40 a.m., primarily high-explosive and shrapnel types, concentrated in the East End and near Liverpool Street Station in the City of London. Approximately 72 bombs fell in a tight area. The raid caused 162 civilian deaths and 432 injuries; the highest casualties from any single air raid on Britain in the entire war.
A particularly horrific incident occurred when a 50 kg bomb struck Upper North Street School in Poplar. It passed through upper floors (killing at least one older child) before detonating in the infants' classroom on the ground floor, where dozens of young children (mostly aged 4–6) were present. 18 children died (16 instantly or soon after, with two more later; most victims were 5–6 years old), and around 37 were seriously injured. This was the single deadliest incident of the raid.
This was not the first Gotha raid on Britain (an earlier one targeted Folkestone on May 25th), but it was the first major one on London itself. It highlighted the vulnerability of cities to strategic bombing and led to public outrage, improved air defences, and later raids.
The raid underscored the shift from Zeppelin to heavier-than-air bomber warfare and the emerging reality of total war on civilian populations. A memorial to the 18 schoolchildren was later unveiled in Poplar Recreation Ground.