NATO launched a new exercise dubbed Eastern Sentry on Sept. 12 in response to the ongoing joint Russia-Belarus military exercise dubbed Zapad (West), which involves thousands of troops, naval maneuvers in the Baltic Sea, and simulated nuclear strikes. Yet two US military observers were invited to Belarus to observe the Zapad exercise, standing on a viewing platform to review forces from the same Russian army that is fighting in Ukraine. This comes shortly after the United States lifted sanctions on Belarusian state-owned airline Belavia, while the regime of Alexander Lukashenko released 52 political prisoners, including an employee of the EU delegation in Minsk. (Ukrainska Pravda, Air & Space Forces, National Security Journal, NYT, DW)

But the freed Belarusian prisoners are protesting that they were expelled to Lithuania in the US-brokered deal and not given the choice to remain in their own country. Additionally, many have noted that they were almost due to be freed anyway. Veteran dissident and one-time Belarusian presidential candidate Mikola Statkevich, released from prison on Sept. 11 as part of the deal, has been returned to a penal colony at Hlybokaye after refusing to accept exile to Lithuania. (The Guardian, The Insider)

The military maneuvers follow an alarming rise in brinkmanship on NATO's eastern flank.

Poland requested an emergency meeting of the UN Security Council and invoked Article 4 of the NATO treaty—mandating urgent talks among alliance members—after an incursion of at least 19 Russian drones into the country's airspace on Sept. 10. The drones were intercepted by Polish and Dutch fighter jets, but not before a private home was struck and damaged in Lublin province. Russia denied targeting Poland, while Belarus, where some drones entered from, said they had "lost their course" because they were jammed. Poland is calling for NATO to impose a no-fly zone over its territory. (AP, CNN, Politico, TVP World)

"Russia's war is escalating, not ending," European Union foreign policy chief Kaja Kallas told reporters in Brussels after the drone incursion. "What Putin wants to do is to test us. What happened in Poland is a game changer." (AP)

Three days later, Romania scrambled two F-16 fighter jets after detecting a drone that had breached its airspace during a Russian attack on Ukraine. The jets followed the drone until it returned to Ukrainian airspace. (France24)

This, in turn, followed new outbursts of Russian threats to use nuclear weapons.