"We have just taken another step forward in adapting NATO to our changed and more challenging security environment," Secretary-General Jens Stoltenberg said in Brussels, Belgium.
In light of Russia's involvement in eastern Ukraine and Moscow's recent decision to upgrade its military, including its nuclear arsenal, NATO is "carefully assessing the implications of what Russia is doing, including its nuclear activities," Stoltenberg said.
Stoltenberg also said the alliance is "working on how to deal with hybrid threats, including through close cooperation with the European Union," the organization said.
The Response Force currently has 13,000 troops and a new Very High Readiness Joint Task Force -- also known as the Spearhead Force -- will have 5,000 troops.
NATO isn't engaging in Cold War-style tactics, Stoltenberg said.
"We do not seek confrontation, and we do not want a new arms race," he added.
The multinational alliance has been conducting several military exercises recently. One took place last week in Sweden, and Russia's foreign ministry on Monday accused NATO countries of "sliding into a new military confrontation with destructive consequences."
About the same time, Russian President Vladimir Putin announced the addition of 40 intercontinental ballistic missiles to Russia's nuclear arsenal.
New small HQs
NATO also will set up six headquarters in Bulgaria, Estonia, Latvia, Lithuania, Poland and Romania. They will employ about 40 people each. A Joint Logistics Headquarters, to help manage the rapid movement of forces, will be established.
The U.S. military will position dozens of tanks, Bradley armored fighting vehicles and self-propelled howitzers in those six nations, Defense Secretary Ash Carter said Tuesday. Carter said the equipment will be moved around Europe for training and exercises.
One analyst, retired Brig. Gen. Mark Kimmitt, said the size of the armor deployment Carter announced Tuesday showed it was more symbolic than strategic.
During the Cold War, the United States had the same amount of armor, a brigade, stationed in just one small part of what was then West Germany, said Kimmitt, the former military assistant to the Supreme Allied Commander in Europe.
"We are now talking about taking one brigade combat team and splitting it among these six countries. That should hardly be seen as a threat to Russia," Kimmitt said.
But the symbolism was important, he said.
"We're sending a message of assurance to our NATO allies. We have obligations, under the NATO treaty, to defend those countries if attacked. I think those countries in the region are going to be welcoming the positioning of these -- this equipment into their countries," Kimmitt said.