TORUN, Poland — About 2,000 NATO troops from the U.S., Britain, Portugal and Poland conducted an airborne training operation on Tuesday as part of the biggest exercise performed in Poland since the 1989 end of communism and amid concerns over Russia.

Scores of U.S. troops and then military vehicles parachuted into a spacious, grassy training area on the outskirts of the central city of Torun. The force’s mission was to secure a bridge on the Vistula River as part of the Polish-led Anakonda-16 exercise that involves about 31,000 troops and runs through mid-June.

Nineteen NATO member nations and five partner nations are contributing troops to the exercise that will train and test their swift joint reaction to threats on land, sea and in the air.

In a complex operation that was precisely planned and timed, troops of the U.S. Army’s 82nd Airborne Division flew directly from their U.S. base in Fort Bragg, North Carolina. Their Boeing C-17 Globemaster transport aircraft were refueled in midair. The British troops flew from a NATO base in Ramstein, Germany, while the Poles arrived from their base in Krakow, in southern Poland.

The coalition’s head of the exercise, U.S. Lt. Gen. Benjamin Hodges, said the exercise represented the commitment of the participating countries to “stability and security in Europe.”

“We want as many to see what we are doing as possible so that they won’t be nervous,” Hodges said, to stress the exercise’s transparency.

Russia considers the presence of NATO troops close to its border as a security threat. President Vladimir Putin’s spokesman, Dmitry Peskov, said Tuesday in Moscow that the military exercise in Poland “does not contribute to the atmosphere of trust and security on the continent.”

Poland and other nations in the region, as well as NATO leaders, say that any military presence or exercises are purely defensive and deterrent measures.

The drill is being held just weeks before NATO holds a crucial summit in Warsaw expected to decide that significant numbers of NATO troops and equipment will be based in Poland and in the Baltic states.

The exercise “confirmed that we can count on our friends who are capable of flying over the Atlantic to be here with us in a matter of hours,” said Polish Gen. Miroslaw Rozanski, deputy commander of the exercise. “We can look into the future with calm. We have good allies and good partners.”