In the span of 24 hours, the war raging for more than two years in Ukraine has intensified significantly.

After a massive barrage of drone and rocket attacks struck their territory overnight into Sunday, and as missiles continued to fall the following evening, U.S. President Joe Biden authorized Ukrainian armed forces to use American weaponry against targets deep into Russia, according to sources reported by the Associated Press.

The Biden Administration’s change in policy comes after what Ukrainian President Volodymyr Zelenskyy described as a “massive combined attack” that “targeted all regions of Ukraine,” killing several people and leaving parts of the country without power.

“This morning began with one of the largest Russian strikes on Ukraine. 210 missiles and drones, including aeroballistic and hypersonic missiles, as well as dozens of Shahed drones, were launched. All of them targeted civilian infrastructure — critical facilities like power plants and transformers,” Zelenskyy shared via social media.

“This evening, a Russian missile hit a nine-story residential building. There are confirmed fatalities, including children. Many people are wounded. Emergency services are on the scene, doing everything to save lives. But what is still missing — and desperately needed — is the principled reaction of the world to this evil,” he said.

Biden’s decision, attributed by the Associated Press to “a U.S. official and three people familiar with the matter,” would represent a stark change in the U.S. stance on Ukrainian use of American arms in Russian territory, which before had been restricted to short range use and mostly aimed at retaking occupied parts of Ukraine.

It also comes as Russian President Vladimir Putin has engaged the aid of North Korea in his unlawful war of territorial expansion, and reportedly deployed tens of thousands those troops against Ukraine’s northern defenses.

“The entire world needs them not to turn a blind eye to Russia’s continued terror. Only when the world reacts decisively can the situation change. Russia has involved North Korea in its war—and the reaction has been weak. Russia has continued its terror for nearly 1,000 days—and the world’s decisions are still delayed,” Zelenskyy said Sunday.

According to reporting, Ukraine will be allowed to fire the U.S. made MGM-140 Army Tactical Missile System (ATACMS), a vehicle mounted weapons system capable of firing missiles close to 200 miles, at targets inside of Russia. That’s not enough to threaten Putin in Moscow, but more than enough range for Ukraine to defend their northern border now that North Korean troops are apparently amassing near Kursk.

Russia has been attacking its fellow former Soviet state for a decade, since 2014 when Putin illegally annexed Crimea. The conflict, which continued in a pair of separatist regions during the following eight years, exploded into full-scale war in February of 2022, when the Russian military further invaded the country on three fronts.

Moscow apparently had planned for just days of military actions, but Russian forces have mostly been stalled in their advances by Ukrainian troops and civilian volunteers armed and trained by a global coalition of nations. According to the U.N., the war has displaced more than 10 million Ukrainian civilians and left half again as many in need of humanitarian assistance.

According to a “confidential” Ukrainian estimate of war dead reported by the Wall Street Journal in mid-September, more than 1 million people have died as a result of the war.

In the years that have followed Russia’s invasion of their democratic neighbor, according to the Department of Defense the U.S. has “committed approximately $56.3 billion in security assistance to Ukraine through both presidential drawdown authority and the Ukraine Security Assistance Initiative.”

Russian President Vladimir Putin said in September that use of U.S. long range precision weapons against Russia would be considered an escalation akin to an attack by all of NATO.

“If this decision is made, it will mean nothing less than the direct participation of NATO countries, the United States, and European countries, in the war in Ukraine,” Putin said.

The U.S. policy shift comes as Biden closes out a trip to South America for a climate summit and bilateral meeting with Chinese President Xi Jinping, when the outgoing president apparently called for China to put more pressure on North Korea to stay out of the conflict in Europe.

National Security Advisory Jake Sullivan said that Biden used the meeting to reiterate “his grave concern over the fact that the (Democratic People’s Republic of Korea) has deployed a significant number of troops to western Russia to participate in the battle against Ukraine, in the war against Ukraine.”

“President Biden really underscored his view that this is a deeply dangerous development, both in the European view, the introduction of a foreign army, and on the Korean Peninsula, with deepening cooperation between Russia and the DPRK likely to enhance the possibility of provocative behavior by the DPRK,” Sullivan said.

Zelenskyy, during a radio interview on Friday, told his people that the war will “end faster with the policy of this team that will now lead the White House,” referring to the reelection of former President Donald Trump.