With 41 military aircraft impacted, the Ukrainian drone attack was described by some commentators as Russia's "Pearl Harbor." The attack on Pearl Harbor in December 1941 was a surprise air raid by Japan on the U.S. during World War II. Kyiv's assault follows ground advances by Moscow troops in recent days in Ukraine's Sumy border region.

Ukraine security service sources tell BBC bombers "are burning en masse" - as Russia confirms Kyiv's drone attack.

The Security Service of Ukraine conducted a large-scale operation targeting four Russian military airfields on Sunday, an SBU source confirmed.

Ukraine has carried out large-scale drone strikes against four airbases deep inside Russia, destroying multiple combat planes, according to a source in the Ukrainian Security Service (SBU).

Kyiv also suffered a damaging blow when a Russian missile struck a Ukrainian military training base, killing at least 12 soldiers. Hours before that strike, Russia launched what Ukrainian officials said was the largest combined overnight aerial assault on the country since the start of the war.

The attack followed a night of bombardment, with Russia launching 472 drones, Ukraine’s air force said. Earlier Sunday, Ukraine’s army said a Russian missile strike on an army training unit killed at least 12 Ukrainian service members and injured 60.

Russian President Vladimir Putin signed a decree that forces Ukrainians to legalize their status in occupied territories — or leave. Already, many Ukrainians had been forced to accept Russian citizenship in occupied areas to maintain their homes or access to health care and education.

By making harsh, uncompromising demands in peace talks with Ukraine while continuing to pummel it with waves of missiles and drones, Russian President Vladimir Putin is sending a clear message: He will only accept a settlement on his terms and will keep fighting until they’re met.