The Defence Secretary has told Forces News the UK "should never underestimate Russia", during a visit to British troops deployed to Estonia.
More than 900 UK soldiers are in the Baltic country as part of NATO's Enhanced Forward Presence (eFP) programme - designed to strengthen Euro-Atlantic security and deter adversaries, close to the border with Russia.
Ben Wallace said the UK should be concerned about Russia "using" its "military muscles" and warned the UK must be aware of the threat posed, citing the nerve agent attack in Salisbury in 2018 and "subthreshold activities" against systems of both the UK and its allies.
"We hope the Russian government takes Russia to a place that is in the rule of law," he said.
"But at the moment, with the poisoning of [Alexei] Navalny, the opposition leader, [and] with activity in Belarus, we should all be concerned."
During the visit, Mr Wallace was given a tour around the alliance's Tapa base.
While Mr Wallace, who sat down for a meal with the soldiers, said he was "delighted to be able to pass on all our thanks" to the personnel deployed in the country over Christmas, he also explained why the deployment is so vital for defence.
He told Forces News the soldiers are there to "reassure and help reinforce" Estonia’s efforts to ensure both its sovereignty and "NATO’s frontline is respected".
"I think the best way to send a message to Russia is solidarity, which is what we saw after the Salisbury poisoning," he added.
"We’re here to show solidarity with the Baltic states and will continue to do so."
5 Rifles are leading the NATO battlegroup in the country, supported by soldiers from Denmark, Estonia and other British units.
Soldiers gave Mr Wallace a demonstration of the capability of the Challenger II battle tanks deployed on the mission.
During the visit, Mr Wallace also held meetings with Estonian Prime Minister Juri Ratas, Minister of Defence Juri Luik and members of the country's National Defence Committee.
Mr Wallace reaffirmed the UK would maintain its presence in the country for as long as necessary, with the two nations agreeing to continue its close defence relationship.
As well as being NATO allies, the UK and Estonia are both members of the UK-led Joint Expeditionary Force and the Northern Group of north European Nations.
In addition to the Army’s presence, the RAF has been deployed to the Ämari airbase in the north of the country for NATO Baltic Air Policing in 2016 and 2019.
Soldiers from both countries have also previously fought side-by-side in Afghanistan and are currently supporting efforts to bring security and stability to the Sahel region in Africa.