That campaign now seems to be migrating into the skies above Europe. For decades Russia has occasionally strayed into the national airspace of NATO allies, which follows national borders and extends 12 nautical miles from a country’s shoreline.

Two NATO officials, who asked for anonymity to discuss sensitive operational matters, told NBC News U.S. fighter jets were taking off for assignments somewhere in Eastern Europe.

Amidst the brewing tensions in Europe, Danish authorities reported that they had detected multiple drones at several military sites overnight.

Without firing a shot, Putin has over the past week managed to bring the war in Ukraine to NATO’s European borders.

Russian Foreign Minister Sergey Lavrov warned, 'Any aggression against my country will be met with a decisive response.'

BRUSSELS (AP) — Since Russian President Vladimir Putin ordered the invasion of Ukraine in 2022, NATO has focused on trying to deter an attack on its own territory and avoid all-out war with nuclear armed Russia. Now the time has come for NATO to defend itself, and European allies might have to do it alone, experts and leaders say.

Calls to "close the skies" over Ukraine — the rallying cry of pro-Ukraine demonstrations in early 2022 — are resurfacing after a wave of Russian airspace violations against NATO members. These incursions have put European countries on edge and raised questions about the alliance’s ability to counter Russian drones and aircraft.

U.S. allies called an emergency meeting of the U.N. Security Council after a series of incidents raised alarm about growing Russian threats to Europe.