The Institute for the Study of War (ISW) reported this in its September 10 briefing.Analysts cited a statement by Prime Minister Donald Tusk, who noted that, for the first time, a significant number of Russian drones entered Poland from the Belarusian direction, and their flight path was unusual. He explained previous incidents as operator errors, disorientation caused by Ukrainian electronic warfare systems, or minor provocations by Russia.ISW noted that the incursion of at least 19 drones in a single night from September 9 to 10 is significant and is roughly three times the total number of munitions that have fallen in Poland over the course of the war. It is considered unlikely that such a number entered Polish airspace accidentally or due to an operator’s technical error.Analysts also drew attention to the words of a Polish military official to Reuters, who stated that at least some of the drones were Gerbera decoy drones. On July 10, Polish journalist Marek Budzisz reported on an unspecified-source report published on July 2, according to which Ukrainian forces had found Polish and Lithuanian SIM cards in Russian drones. According to the report, this could indicate that Russia was preparing trial strike corridors in Poland and Lithuania.“Russia may have been preparing for the September 9-10 incursion for months, further indicating that the incursion was not an accident or the result of Ukrainian EW interference,” the ISW report states.The Institute suggests that Russia is attempting to assess the capabilities and reactions of Poland and NATO, hoping to use this information in future conflict scenarios with the alliance.According to ISW, Russia is making “multipronged efforts” to prepare for a potential future war with NATO. Testing NATO’s technical capabilities and political resolve may be part of this campaign, and Russia “appears to be growing bolder in terms of what sort of escalation it is willing to test,” analysts conclude.Russian Shaheds in Polish airspace. BackgroundPolish Armed Forces’ Operational Command put air defense systems and aviation on highest alert due to Russia’s night attack on Ukraine: Russian drones violated the country’s airspace.As a result of a Russian attack on the night of September 10, drone debris fell on a residential building in a village in Poland’s Lublin Voivodeship. No one was injured.Ukraine's President Zelenskyy says Ukraine is ready to help Poland develop an alert and air defense system. Meanwhile, European Commission President von der Leyen announces the EU will build a “drone wall” on the Russia border.Ukrainian President Volodymyr Zelenskyy commented on the violation of Poland’s airspace by Russian drones, stating that Kyiv had warned Warsaw about the UAV movements.On Wednesday, September 10, NATO activated Article 4 of the North Atlantic Treaty after Russian drones violated Polish territory.