NATO Secretary General Jens Stoltenberg announced allies will agree to increase the size of the alliance’s rapid reaction force to 300,000 troops. That is nearly eight times higher than the current 40,000 soldiers serving in the force. Speaking in Brussels Monday, Stoltenberg described the move as part of the “biggest overhaul of collective defense and deterrence since the Cold War.”

“We will enhance our battle groups in the eastern part of the alliance up to brigade levels,” Stoltenberg said. “We will also boost our ability to reinforce in crisis and conflict, including with more pre-positioned equipment and stockpiles of military supplies.”

Back in February, NATO allies agreed to send thousands of troops, backed by air and naval support, to protect allies near Russia and Ukraine. The alliance decided at the time to send parts of the its rapid reaction force to the alliance’s eastern flank, marking the first time the force had been used in a defense role.

An immediate response from Russia to the announcement was not available. Back in December, Russia published a set of security demands that included rolling back NATO’s military deployments in Central and Eastern Europe.

Stoltenberg’s announcement came as he was previewing this week’s NATO summit in Madrid. At the summit, the NATO allies are expected to announce further support for Ukraine to defend itself against Russia’s invasion.

“I expect it will make clear that allies consider Russia as the most significant and direct threat to our security,” Stoltenberg said. Leaders of the group of seven also pledged their support to Ukraine at their own summit Monday.

In addition to the rapid reaction force expansion, another expected highlight from the NATO summit involves allies addressing “the challenges that Beijing poses to … security, interests and values.” Russia and China have been considered two of the largest threats to the United States in recent years.

“There is increasing convergence, both at the G7 and at NATO, around the challenge China poses and around the need — the urgent need for consultation and especially alignment among the world’s leading market democracies to deal with some of those challenges,” National Security Advisor Jake Sullivan said at a Monday press gaggle.

The Associated Press contributed to this report.