Ukraine reportedly attacked two Russian air bases by drones on Monday, flying hundreds of kilometers into Russian air space. Another drone attack set fire to an oil tank at a third Russian air base on Tuesday.

Ukrainian officials have not claimed responsibility for the drone attacks, according to The New York Times (NYT), but Ukrainian presidential adviser Mykhailo Podolyak said what comes around goes around.

“The Earth is round – discovery made by Galileo. Astronomy was not studied in Kremlin, giving preference to court astrologers,” Podolyak tweeted. “If it was, they would know: If something is launched into other countries’ airspace, sooner or later unknown flying objects will return to departure point.”

The Dyagilevo airfield in Ryazan Region and the Engels airfield in Saratov Region were targeted on Monday. On Tuesday, a drone attack occurred 80 miles from the Ukrainian border near a Russian air base in the Kursk region.

If it turns out that Ukraine’s forces were behind the most recent attack, it would be another sign that Kyiv wants to bring the war closer to Moscow and President Vladimir Putin, according to NYT.

After the drone attacks on Monday, Russia fired missiles at Ukraine. This cut power to half of Kyiv’s capital city and worsened rolling power outages throughout the country. At least 10 rockets were aimed at Kyiv on Monday, NYT reported.

“Unfortunately, there are victims,” Ukrainian President Volodymyr Zelenskyy said. “As of this time, there are four people killed by Russian strikes today. My condolences to families and friends.”

Retired Australian Army officer Mick Ryan suggested that the strikes inside Russia were symbolic, as Dyagilevo is roughly 100 miles from the Russian capital. Ryan said the shelling delivered a mental blow to Russian citizens who thought they were insulated from the effects of the invasion of Ukraine.

Even though the Ukrainian drones probably did not do much physical damage, they are likely a morale booster for the Ukrainians as the ground war slows down for the winter and Russia allegedly continues attacking energy infrastructure from the air.

U.S. Secretary of State Antony Blinken recently predicted that the 10-month-long conflict in Ukraine “will end almost certainly with diplomacy,” but he added that a ceasefire that freezes the current battle lines would be “a phony peace.”

Blinken called instead for “a just and durable peace.”

Kremlin spokesman Dmitry Peskov responded, “That the outcome should be ‘a just and durable peace’ — one can agree with this. But as for the prospects for some kind of negotiations, we don’t see them at the moment; we have repeatedly said so.”

Since Russia invaded Ukraine nine months ago, Putin and U.S. President Joe Biden have not talked, according to Reuters.