By the summer of 1955, the FLN's guerrilla campaign was failing. French counterinsurgency pressure had reduced the movement to near-irrelevance, and only one of its regional sections -- Wilaya II, led by Youcef Zighoud -- could mount any offensive at all. Popular support remained low. Many among the Algerian Muslim elite still believed in negotiating with France for reform rather than fighting for independence. Zighoud calculated that an attack on European civilians would provoke a savage French reprisal, which would in turn destroy the fragile coexistence between the pied-noir settlers and native Algerians. He was willing to sacrifice Algerian lives -- sending barely armed civilians against military targets and fortified towns -- to achieve that political end. Even senior FLN leaders, including Abane Ramdane and Larbi Ben M'hidi, later condemned the decision as reckless and inhumane.

The coordinated raids struck across the Constantine region. In Philippeville -- now called Skikda -- a mob of several thousand civilians led by FLN members assaulted the city with firearms, farming tools, and makeshift bombs. Europeans were attacked in the streets. Police forces and paratroopers suppressed the uprising, but not before 14 officers died. At the El-Halia pyrite mine, where 130 Europeans and 2,000 Muslims lived and worked side by side, an FLN-led mob arrived at 11 a.m. while the European men were underground in the mines. The attack killed 37 Europeans, mostly women and children. In Constantine, eight FLN commandos launched targeted assassinations -- killing Allouah Abbas, a moderate politician and nephew of Ferhat Abbas, in the pharmacy he owned. Bombs exploded in the Jewish quarter, killing two and wounding dozens.

What followed was disproportionate beyond measure. French paratroopers arriving at El-Halia rounded up 80 Algerian men and shot them without investigation. At El Khroub, 60 captured insurgents were executed the same day. In Philippeville itself, the city's stadium became an interrogation center where thousands of Algerian males were rounded up, briefly questioned, and executed without trial. A French journalist, Robert Lambotte, photographed the lined-up bodies and published the image in the communist newspaper L'Humanite, sparking outrage across France. Pied-noir vigilante militias, armed by Philippeville's mayor, began killing Muslims at random. The total death toll of French retaliation remains disputed -- the official figure of 1,273 is widely considered a gross undercount. Historian Benjamin Stora estimates 10,000 Muslims were killed by French military and pied-noir militias in the Constantine region. The FLN claimed 12,000.

Zighoud's terrible gamble succeeded. The massacre of Europeans followed by the vastly larger massacre of Algerians destroyed any possibility of a peaceful middle ground. Three weeks after the attacks, 61 prominent Algerian Muslim politicians -- moderates who had previously believed integration with France was possible -- signed a public declaration condemning the 'blind repression' and declaring that the vast majority of Algerians had become nationalists. By late 1955, FLN fighters in the Constantine region had tripled. Jacques Soustelle, the Governor of Algeria who had championed conciliation, visited El-Halia and emerged convinced that negotiation with the FLN was impossible. Albert Camus, the pied-noir intellectual who had advocated for Algerian rights, rejected the FLN entirely after learning of the atrocities against children. The war that followed would last seven more years, cost hundreds of thousands of lives, and end with Algerian independence in 1962 -- but the path to that outcome was set on a single August day in 1955.