For the first time in the history of the alliance, NATO has activated part of its 40,000-troop strong response force to secure member nations near the borders of the Russian-Ukraine war.

At a press conference announcing the unprecedented deployment of troops, NATO Secretary General Jens Stoltenberg warned Friday that "the Kremlin's objectives are not limited to Ukraine."

"We are deploying [the NRF] to ... prevent any miscalculations, any misunderstandings that we are not ready to protect and defend all our allies," Stoltenberg said. "This is something that all allies have agreed to do."

NATO Response Force troops will deploy "on land, at sea, and in the air" in eastern Europe for the purpose of collected defense, Axios reports.

The secretary general explained that while the size of the NRF has tripled since 2014, not all of its forces would be deployed. He also said that NATO countries would be providing Ukraine with arms and air-defense systems at the request of Ukrainian President Volodymyr Zelenskyy's government.

Stoltenberg told reporters that the eastern flank allies "are extremely concerned" with the events unfolding in Ukraine.

"They are close to the fighting in Ukraine, and they also border Russia, and they've seen not only the military buildup and the ongoing war in Ukraine, but also seen the very threatening rhetoric because this goes far beyond Ukraine," Stoltenberg said.

"Russia's attack on Ukraine is more than an attack on Ukraine. It's a devastating horrendous attack on innocent people in Ukraine, but it's also an attack on the whole European security order. And that's the reason why we take it so extremely seriously," he added.

U.S. President Joe Biden has also deployed troops to eastern Europe to secure NATO countries bordering the conflict. The president has made clear that these troops are being deployed as a defensive measure, and they will not be sent into Ukraine to engage with Russian forces.

NATO Supreme Allied Commander Gen. Tod Wolters said the activation of response forces was "historic" in a statement.

"This is an historic moment and the very first time the Alliance has employed these high readiness forces in a deterrence and defense role. They represent a flexible, combat credible force that can be employed in multiple ways and we are utilizing fully their inherent agility," Wolters said. "These deterrence measures are prudent and enhance our speed, responsiveness and capability to shield and protect the one billion citizens we swore to protect."

In a statement released Friday morning, Zelenskyy thanked NATO for its support but requested more from the alliance to defend against the Russian invaders.

"We are alone in defending our country. Who is ready to defend us together with us? Honestly, I don't see any," Zelensky said. "Who is ready to give Ukraine a guarantee of joining NATO? Honestly, everyone is afraid."