For more than three years, Ukraine has waged an almost nightly battle against Russian attack drones.

NATO on Wednesday got a taste of that fight.

Polish authorities said they detected 19 violations of their airspace, prompting a million-dollar response as fighter jets were scrambled and Patriot air defense systems placed on alert.

Up to four drones were shot down with the help of NATO allies.

The incursion showed NATO's vulnerability to drone warfare.

Russian authorities said they didn’t target Poland, and Belarus, a close ally, said some of the drones “lost their course” because they were jammed.

Nonetheless, several European leaders and experts said Poland was deliberately targeted.

If one or two drones crossed into Polish airspace, it could have been a “technical malfunction,” but it “defies imagination that it could have been accidental” when there were 19, said Poland's Foreign Minister Radek Sikorski.

"There is an indication that perhaps somewhere the detection capability was lacking, enabling these drones to fly into Polish airspace," said Thomas Withington, an expert in electronic warfare at the Royal United Services Institute in London.

A goal, he suggested, could have been to test NATO's reaction and ability to respond to drones.

"My feeling again with the information I've got at the moment was I think this was a deliberate, it could well have been a deliberate action by the Russians and the Belarusians, possibly to see how good Polish counter drone reaction was, see how good their air defence system was."

"Sadly, incidents such as we've seen in Poland yesterday are only likely to increase, that we have to be ready for those and we have to be prepared to act in a whole-of-society approach to the continued Russian threat," he added.

Since January, Russia has fired at least 35,698 attack drones at Ukraine according to an Associated Press analysis of data from the Ukrainian air force.

Polish airspace has been violated multiple times since the beginning of Russia’s full-scale invasion of Ukraine in February 2022.

Fragments from Ukrainian missiles killed two people in Poland in 2023, while drones have strayed into Poland, Romana and Moldova as well as the Baltic states of Latvia, Lithuania and Estonia.

But until Wednesday, no NATO country had sustained multiple incursions into its airspace. It was the first time NATO airpower was engaged against enemy targets inside a NATO country.

Drone fragments were found about 554 kilometers (344 miles) into Polish territory — deeper than any previous incursion.