The Biden administration announced on Thursday that it will send an additional $600 million in military aid to Ukraine. The U.S. is rushing more weapons to fuel Kyiv's counteroffensive, which has regained significant swaths of the beleaguered country and forced Russian troops to retreat.

According to the White House, this is the twenty-first time the Defense Department has delivered guns and other equipment to Ukraine.

The shipment will include more of the ammunition and equipment that helped Ukrainian forces repel Russian forces in parts of the east and south.

Secretary of State Antony Blinken stated, "With admirable grit and determination, the people of Ukraine are defending their homeland and fighting for their future,"

"The capabilities we are delivering are carefully calibrated to make the most difference on the battlefield and strengthen Ukraine's hand at the negotiating table when the time is right," he said in a statement.

The decision to move swiftly on new aid — on the heels of a nearly $2.9 billion infusion of aid and financing support announced last week and more than $3 billion announced in late August — underscores the U.S. determination to ensure that Ukraine can sustain its stunning counterattack, which was launched at the beginning of the month.

This most recent investment included $2.2 billion in long-term military financing revealed by Secretary of State Antony Blinken on his visit to Ukraine last week, as well as a $675 million weapons package released by Defense Secretary Lloyd Austin in Europe on the same day.

The United States declared that the $2.2 billion that Blinken promised in Kyiv is for Ukraine and 18 of its neighbors, including NATO allies and regional security partners, who are potentially at risk of a future Russian assault.

Moscow's recent military defeat in northeast Ukraine was its worst since it withdrew its soldiers from territories near Kyiv more than five months ago.

The current shipment of weaponry systems puts the entire amount of U.S. aid to Ukraine since the inauguration of President Joe Biden at approximately $15.9 billion.

Noting that Russia still has large troops and resources, U.S. officials observing the counteroffensive have avoided prematurely declaring victory. And they are wary of what Vladimir Putin, the president of Russia, might do to alter the tide.

But U.S. authorities have also made it apparent that precision weaponry and rocket systems provided by the U.S. and its partners — such as the High-mobility Artillery Rocket System, or HIMARS, and the High-speed Anti-radiation Missile, or HARM — have played a crucial role in the rapid shift in momentum.