NATO went on its highest alert last Tuesday around 9:30 p.m. local time after Russian drones entered alliance territory, in the bloc’s most serious security incident in decades, according to a reconstruction of events that night by German newspaper WELT.

By the end of that night, more than two dozen drones penetrated 250 kilometers into NATO airspace over Poland, some of them heading toward a key NATO logistics hub for Ukraine, according to the reconstruction by WELT, a sister publication of POLITICO in the Axel Springer Group.

At 8:17 p.m., an alarm sounds at the NATO air surveillance station in Uedem, a small German town close to the Dutch border. The soldiers detect a swarm of attack drones flying over Ukraine.

Some of these drones are Russian-fabricated long-range combat models with a 2.5-meter wingspan, traveling at about 160 km/h and a range of 600 kilometers, as Polish investigators find out later.

Fifty minutes later, at 9:06 p.m., concern grows as the drones continue to fly toward Poland, five of them headed toward a NATO logistics hub in Rzeszów. NATO forces issue a yellow alert.

At 9:26 p.m., the first drones are entering NATO territory. NATO combat units are on alert. Four minutes later, the alert level for a possible air raid jumps to red.

At 10:04 p.m., NATO interceptors, German Patriot missile-defense systems and other units are ready to intervene. Poland deploys F-16 fighter jets and several helicopters, including a Black Hawk.

At 1:13 a.m. Wednesday, the first drone is shot down by a Dutch F-35 fighter jet.

By 4:44 a.m., the last drone that poses a threat is eliminated. Several of the drones crashed without being shot down. One drone crashed into a house, but the debris did not injure anyone on the ground. 

A high-ranking NATO official told WELT that they don’t believe that the drones entered NATO airspace by accident, but rather were deliberately sent there.

Poland invoked Article 4 of the NATO treaty, which says that NATO partners will consult together when in the opinion of a member country the territorial integrity of the alliance is threatened.