The U.S. Army has been training troops in the Baltic states to help prepare them for hybrid warfare tactics. Concerns that Russia could make an attempted land-grab have led Latvia and Poland to train with Special Forces and the National Guard in West Virginia in the Ridge Runner program. These exercises focused on unconventional and hybrid warfare strategies in order to help the two nations build up their military strength. The units worked on recognizing and slowing down the attacks from the beginning, such as training as forward observers and learning to destroy important transportation infrastructure.
Source: https://nationalinterest.org