Operation Atlantic Resolve

Operation Atlantic Resolve are ongoing efforts in response to Russia's actions in Ukraine, mainly the War in Donbass. It is funded under the European Reassurance Initiative. All U.S. efforts in support of NATO fall under the umbrella of Operation Atlantic Resolve. The U.S. took several immediate steps to demonstrate solidarity with NATO, such as augmenting the air, ground and naval presence in the region, and enhancing previously scheduled exercises. The U.S. is taking measures to enhance NATO military plans and defense capabilities and remains committed to maintaining a persistent presence in Eastern Europe.

In the middle of March 2015, a US Army spokesman in Wiesbaden announced that a convoy of armored fighting vehicles (amongst them Strykers) would – after manoeuvres in Poland, Estonia and Lithuania – return via road to their garrison at Vilseck. The roadmarch started a week later.

The aerial assets are mostly deployed to Ämari Air Base, Graf Ignatievo Air Base and Papa Air Base.

The first aerial units were the 159th Expeditionary Fighter Squadron (159th EFS) with McDonnell Douglas F-15C Eagle's and the 123d EFS with F-15C's and a single F-15D from April 2015 who stayed for six months.

This was added to by the following units:

The new shipment of forces - 3,500 troops from the 4th Infantry Division, 87 tanks and 144 Bradley fighting vehicles - will gather first in Poland, then fan out across seven countries from Estonia to Bulgaria. They will be headquartered in Germany.

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Wikipedia