In late March, Donald Tusk, the Polish prime minister, made a plea to Nato: put 10,000 troops in Poland, permanently, he asked.

But to the consternation of many in Poland and the Baltics, Angela Merkel, the German chancellor, last week slapped down any notion of Nato boots in a long-term positioning on eastern European soil during a visit to Latvia.

In the wake of Russia’s land-grab in Ukraine, the debate over how Nato should respond has been an impassioned one that threatens to divide the alliance.

“What Ukraine has done is put in perspective Russia’s policy, which is threatening to overturn the basic principles of European security,” says Michael Clarke, director-general of the Royal United Services Institute in London. “There’s almost a view for some that we are walking into a new Cold War or a new 1930s.”

At its biennial summit this week, Nato will hope to bridge the member states’ divisions with the unveiling of its new “readiness action plan”, the result of weeks of detailed negotiation among alliance ambassadors in Brussels.

The plan is not yet set in stone and, hawkish critics warn, is at risk of degenerating into a feat of linguistic acrobatics with little substance.

The key sticking point has been whether Nato should discard – or bend – rules laid out in treaties such as the Nato-Russia founding act and the Conventional Armed Forces in Europe Treaty and subsequent documents, which proscribe “new” permanent deployments of troops, effectively ruling out bases in eastern Europe and the Baltics. Though Russia itself declared a moratorium on the CFE Treaty in 2007, Nato members such as Germany believe the alliance should still abide by the spirit of the document.

In crafting its new policy, Nato has therefore walked a careful line on troop deployments.

“We are not going to use any reference, not even in colloquial communication, on permanent basing,” says one senior Nato official. “We will talk about ‘appropriate presence’.”

What such “appropriate presence” may amount to has been left deliberately open-ended, the official added. The crucial shift in language, for the alliance, is on how the readiness plan will focus on Nato’s “frontier” – a reference to the Baltics and eastern Europe. The plan calls for it to be strengthened with improved swift deployment capabilities and increased military exercises and deployments in frontier states.

“The deal with the Russians that there wouldn’t be any forward Nato positions in these ‘no mans’ states’ cannot be sustained,” says Sir Malcolm Rifkind, the chair of Britain’s parliamentary intelligence and security committee. “Nato assets must be positioned in all Nato countries that require them,” he says.

Sven Mikser, Estonia’s defence minister, told the Financial Times that he wants to see “an Allied presence on our soil as a way of reassurance and deterrence”.

But, Mr Mikser added: “We don’t mean the Cold War-style of a very heavy, static presence. We are not talking of divisions.”

The alliance’s plan will feature a new high-readiness brigade, capable of being deployed in hours and significant propositioning of material in Poland, as well as a permanent command centre at Szczecin on the Baltic coast.

Some of this will dovetail with ongoing Nato work. The US has just begun to put in place its new “European Activity Set”, a battalion-sized arsenal first used in military exercises in June. Currently based in Grafenwoehr in Germany, it will be relatively easy to relocate the EAS to Poland, replicate it there, or augment it.

A more significant part of the plan will be the increased military exercises and deployments.

Nato allies have already ramped up their efforts in the wake of the Ukraine crisis. The US, for example, has deployed 600 paratroopers from its 173rd Airborne Brigade equally divided between bases at Swidwin in Poland, Paldiski in Estonia, Adazi in Latvia and Rukla in Lithuania. Denmark, France and Britain have, meanwhile, sent fighter jets to Amari in Estonia and Malbork in Poland.

But even Nato’s biggest military exercises do not come close to matching the scale of those undertaken on its borders by Russia. Spring Storm, the largest ever Baltic war game in late May, involved 6,000 troops. By comparison, Russia’s emergency war games on the Ukrainian and Baltic state borders in February involved 150,000 troops.

“I don’t think we will go back to a full Cold War-type posture where we had millions of troops involved in exercises on both sides of the Fulda Gap,” says Admiral James Stavridis, who until last year was Nato’s supreme allied commander and is now dean of the Fletcher School at Tuft’s university. But Mr Stavridis predicted a sizeable increase from the slimmed-down exercises of the past decade.