Around 17,500 soldiers from 10 NATO member states are participating in military drills that started on November 7 in Poland and the Baltic states, the Polish Defense Ministry announced.
The ministry said the "Anakonda" exercise is the biggest drill the Polish forces have ever held, with 12,500 Polish troops involved at training grounds in the country. A further 5,000 soldiers from NATO member countries are taking part in Estonia, Latvia, and Lithuania.
The schedule also includes naval maneuvers in the Baltic Sea.
The exercises will continue until November 16 and are aimed at training the individual units to cooperate with each other, the ministry said.
Since the annexation of Ukraine's Crimean Peninsula by Russia in 2014, Poland and the three Baltic states as well as other Eastern European states have expressed concern about their security.
The United States has deployed and rotated troops in the region since the Ukraine crisis began in an effort to deter Russia. NATO has also increased its presence on the eastern borders of those four countries, all of which border Russia.
Poland has been calling for more U.S. military personnel to be deployed on its territory, with Warsaw suggesting to U.S. President Donald Trump recently that he create a permanent base under the name "Fort Trump."