Story highlights NATO Response Force has 13,000 troops, will increase to 40,000

Secretary-General Jens Stoltenberg says the alliance isn't playing Cold War-like games

U.S. is committing armor to be based in six NATO-affiliated nations

(CNN) NATO announced late Wednesday it will triple the capacity of its Response Force to 40,000 troops.

"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.

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