As the Ukraine crisis has intensified over the past six months, Russia has been developing a new form of warfare – inserting special forces, provoking, and slowly, deliberately escalating the conflict. Russian actions flout international law and the agreements that have assured stability in the post-cold war world. But warnings and sanctions have thus far failed. The Nato summit in Wales this week offers the best, and perhaps last, opportunity to halt aggression in Europe without major commitments of Nato forces. But to do so requires a deeper understanding of the situation and much more resolute allied action.

First, Vladimir Putin’s actions against Ukraine haven’t been “provoked”. They are part of a long-term plan to recreate a greater Russia by regaining control of Ukraine and other states in the “near abroad”. Russia is not going to admit that it has invaded because to do so might invite a stronger Nato response. But until Nato governments unambiguously label Russian actions “aggression” and “invasion”, they will have difficulty mustering support for the stronger actions that needs to be taken.

Putin is not likely to be dissuaded by stronger sanctions; while they may disrupt some elements of the Russian economy, and he would of course prefer not to face them, he also uses sanctions himself to strengthen his leverage over those sectors most engaged with the west, and to gain sympathy from his own “electorate”.

Nato must act decisively to strengthen member states that feel threatened by Putin’s actions. Its forces should be permanently stationed in the Baltics, Poland and eastern Balkans. Its rapid reaction forces should be bolstered. Additionally, more demanding military exercises should be held. Nato’s nuclear deterrent must be re-emphasised. Long overdue modernisation should be undertaken. All this requires greater resources, including budget and manpower.

But these are the relatively easy steps. Even if undertaken – and they will take months and years to be implemented – they are unlikely to halt the growing threat, nor will they prevent the demoralisation of our friends in eastern Europe. As we like to say in America, “this is not their first rodeo”. They understand that aggressors are strengthened by their successes. And they know that today Ukraine is fighting on Nato’s periphery for the very same values of freedom, self-government and democracy that Nato espouses. They are asking themselves how courageous Nato will be, confronting a renewed Russian threat, if Nato nations today fear to provide information, military advice and assistance to an independent European state of 45 million fighting a defensive battle merely to regain control its own territory. And, yes, it is open warfare in eastern Ukraine now.

The success of this Nato summit will be measured not simply by its declarations of intent to strengthen alliance members in eastern Europe but, perhaps more importantly, by its willingness to provide Ukraine with the diplomatic, economic and, most immediately, military assistance necessary.

True, there is no “military” solution to Ukraine. The only solution is diplomatic: Putin must be persuaded to cease and desist. But, as we are learning, that persuasion requires not only diplomacy and sanctions, but also assisting Ukraine in creating the military means to defeat Russia’s new war strategy.

Information, training, military advice and hardware provided now will likely save thousands of lives and billions of dollars in the future. This is the time to speak the truth about Russian aggression and to act resolutely in aiding Ukraine to halt it.