Two U.S. senators are warning that Russian President Vladimir Putin is stalling on peace while preparing a fresh military offensive against Ukraine.

A truck pulled in, and drones flew out of it.” From an airbase near Murmansk, in Russia’s far north, came similar stories: “The driver’s running around...drones are flying from his truck toward the base.

The message came after Ukraine’s forces wiped out and damaged 41 of the Kremlin’s nuclear bombers and aircraft, attacking at least four air bases across Russia in a massive operation.

Russian and Ukrainian officials are due to sit down on Monday in the Turkish city of Istanbul for their second round of direct peace talks since 2022, but the two sides are still far apart on how to end the war and the fighting is stepping up.

Since last sitting down with Ukraine to talk peace, Russia has launched four of its five largest drone attacks against the country, killed more than 340 of its civilians and continued to peddle its false narrative about the unprovoked war it has been waging for more than a decade.

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.

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.

NATO members must prepare for a possible attack from Russia within the next four years, Germany's chief of defence has warned.