Cover picture: US Department of Defense
NATO's Exercise Sabre Strike is two weeks of complex training involving 19 countries and 18,000 troops.
Led by the United States in Estonia, Latvia, Lithuania and Poland, its aim is to prove readiness against threats to the region but it is being increasingly viewed by Russia as provocation.
Major General Bill O'Leary, Deputy Commander Field Army, said: “We know there are areas in the world where there is friction.
“What we need to do is we need to make sure that our allies in those countries, in those regions, for example the Baltic States, know that we are here.
“So for us to come along and train with them and understand a bit about the landscape as well – let’s be clear about that we need to understand the terrain - but more importantly working with our allies in those regions to give them more confidence that we’re there just incase they need us.
“And again that’s vitally important for not just our regular forces but for our army reserves as well.”
Now in its eighth year, Sabre Strike is bigger than ever before and has grown considerably – in 2013 there were just 2,000 troops.
Although Moscow has said it sees these large 'war games' near its borders as provocation, NATO forces insist they are just exercises among allies.
But with Russia's annexation of Crimea, and a suspected Russian chemical attack in Salisbury, world threats feed into the training.
For the last two weeks, troops have been training in assaults, security patrols and water crossings. They have also been rehearsing responses to chemical attacks and testing out kit and equipment.