WASHINGTON — To celebrate the 70th anniversary of NATO, Secretary of State Mike Pompeo gathered ministers from all the nations in the military alliance on Wednesday night in the same hall where Harry S. Truman signed the North Atlantic Treaty Organization pact in 1949. “No military alliance in the world can remotely do what we do,” Mr. Pompeo said, hailing NATO’s success.

But the forces pulling that alliance apart were evident everywhere.

The bonds among the core nations that signed the original treaty, which was displayed next to Mr. Pompeo, are fracturing. New members that were once Soviet states are turning authoritarian. This week, the Pentagon blocked delivery of equipment for the alliance’s most modern weapon, the F-35 fighter jet, to Turkey because the NATO nation would not back down on buying Russia’s most sophisticated antiaircraft system.

Vice President Mike Pence declared at the celebration that Germany risked becoming a “captive of Russia” because of its embrace of a direct energy pipeline to Russia.

And missing altogether was President Trump, whom European and American officials alike wanted to keep away from the anniversary for fear he would again raise the idea of pulling out of NATO if other member states did not pay a greater share of the defense burden.