Britain will have just one tank regiment from today, meaning that it will have more horses than tanks, and will only be able to field around tanks in a war.

The Times reports that thousands will gather in Wiltshire today to mark the merger of Britain’s two remaining tank regiments amid concerns that the move could be misguided as tensions with Russia increase.

After a decade fighting insurgents in Iraq and Afghanistan with just light infantry, heavy armour became seen as outdated. However, after Russia’s annexation of Crimea and its continuing actions on eastern Ukraine, there are now calls to change priorities.

Lieutenant-General Sir Andrew Ridgway, a long-serving tank officer who is now Colonel of the Royal Tank Regiment, said: “Going down to the small number [of tanks] that we are going to have in future is taking a risk. But defence capability is like insurance: You don’t have the insurance you want. You have the insurance you can afford. The crucial thing is to get your priorities right, to make sure the things you really need are what you have.”

Colonel Hamish de Bretton-Gordon added: “Recent conflicts in Iraq, Afghanistan and Syria appear to signal the demise of the tank but activities in Ukraine especially and Gaza might suggest this is a little premature.”

This weekend’s merger is especially ironic as it takes place as Britain prepares to commemorate the hundredth anniversary of its entry into First World War. It was during that war that Britain pioneered modern heavy armour, introducing the first ever tank into active service in 1916.

By the end of the First World War, Britain had 25 tank regiments, rising to 44 after World War II.

However, from today there will only be one Royal Tank Regiment, which will have 56 Challenger 2 tanks. Two other regiments – The King’s Royal Hussars and the Queen’s Royal Hussars – will also each have 56, bringing to total number of tanks in the army to 168.

This means tanks the modern British Army now has fewer tanks than horses, and also puts the UK behind many smaller countries, including neutral Switzerland.

General Ridgway said he did not want the number of tanks to fall any further: “We really have reduced to a very low level,” he said.

A spokesman for the Ministry of Defence said: “The Army has been redesigned so that it is more adaptable, agile and can continue to respond to future threats. The amalgamation of 1 and 2 RTR is part of these plans and will not affect our ability to deal with modern threats including the use of a wide range of armoured vehicles and tanks.

“Alongside our allies, we take recent events in Ukraine extremely seriously. That is why we have taken measures aimed at reassuring our Nato allies in Eastern Europe such as UK participation in a major land exercise in Poland involving 1,300 troops and more than 300 military vehicles as announced by the Defence Secretary earlier this week.”