Seven hundred and fifty soldiers are involved in the Operation Cabrit rehearsals ahead of the next British-led NATO Battlegroup to go to Estonia in September.
It will be the British Army's eighth Baltic assignment since 2017.
Operation Cabrit is now one of the Army's largest overseas commitments; it is part of a NATO reassurance mission in a region that borders Russia.
Challenger 2 Operator/Loader, Lance Corporal George Millar, told Forces News: "People have Afghanistan in the back of their minds but the people of my generation that have joined the Army post-Afghanistan you haven't had a chance to go out and sort of prove yourselves, so this will be a good opportunity to do that."
The Foreign Secretary said the UK will continue to stand with Estonia and its partners in tackling "Russia's malign activity" in the Baltic region in March during a visit to Estonia.
Tension has grown in the region since Moscow backed eastern Ukraine rebels and annexed Crimea.
Estonia and the other Baltic States don't want to be next.
Brigadier Paddy Ginn, Commander 20th Armoured Infantry Brigade, said: "They are willing to fight for every inch of territory if they have to and therefore our forces have really learnt the sombre and compelling reason for why they're over in Estonia as an operation.
"Living in hard conditions and squeezing every moment of training out of being in Estonia because they have to be and are ready to fight at a moment's notice."
Lieutenant Colonel Simon Worth, Commanding Officer of the Royal Tank Regiment, explained: "To deliver a credible force, we've got to do the kind of training and deliver the kind of capability that will convince the Estonian people and the rest of NATO that we are really serious about this operation."
The Army describes Sennelager as the best place for its Estonia preparations and is grateful to Berlin for the continuing freedom to train in Germany.
Lieutenant Colonel Simon Worth, Commanding Officer Royal Tank Regiment, told Forces News: "The real value of Sennelager is that it closely reflects the operating environment that we would expect to operate on in Estonia and therefore, for us, it provides an excellent kind of dry run rehearsal that will take us to where we need to be."
The Army's Collective Training Group syllabus is deliberately arduous and demanding to test every battlegroup capability, not just tank crews.
Trooper Charlie Mckinley, Reconnaissance Troop, said: "We've had Challies [Challenger tanks] fire, Warrior infantry fighting vehicles, we've had artillery here getting rounds down as well."
The training also included the live firing of Challenger 2 tanks.
Sergeant Richard Johnson, Royal Tank Regiment Dreadnought Squadron, told Forces News it's an experience "you can never get anywhere else".
"There's nothing that can compare to firing 120-millimetre ammunition on Challenger 2."
3rd Regiment Royal Horse Artillery brought highly mobile 105-millimetre light guns and co-ordinated fire with watching tank crews.
Royal Engineers cleared mines and other obstacles, allowing armoured infantry fighting vehicles to move forward, and deliver troops to their next objectives.
To be effective, a battlegroup must tightly choreograph many different elements.
Brigadier Paddy Ginn, Commander 20th Armoured Infantry Brigade, told Forces News the "beauty" of this exercise is that "we've got the ability to stop, reset, go again".
"That's what training in combined arms manoeuvre warfare gives you.
"You have to have that ability to get things wrong. Stop, reset and go again.
"That's when the real mastery will come."
In September, the Royal Tank Regiment battlegroup in Estonia will also include French troops.