Some 600 troops and 100 military vehicles are expected to be deployed in the area, which is close to Latvia's borders with Lithuania and Belarus. The exercise is aimed at improving cooperation within the multinational alliance in a scenario where they need to protect Europe's eastern border.
Steel Brawler is part of a broader exercise called Defender Europe 2020 which ended up being significantly reduced in scope due to the COVID-19 pandemic.
The drills are scheduled to run through 18 April.
Last year, the bloc announced plans to boost its presence in Poland and the Baltic States in order to contain the so-called "Russian threat". Moscow has repeatedly stressed that a NATO military build-up would undermine regional stability.