NATO has already made its position clear long before the beginning of the conflict: no military intervention in Ukraine that would lead to a direct confrontation with Russia.
Since nobody wants the beginning of the third world war. NATO is therefore supporting Ukraine in every other way possible, but will not intervene on the ground.
De facto, if Ukraine loses this war, but we still have to agree on what that means, we will have to take note of it and deal with it, according to Sylvain Saurel.
We will have to see if Ukraine passes entirely under Russian control, which I strongly doubt, or if Ukraine loses the Donbass and the South of the country.
This would already be a heavy loss, but then the situation would be different.
If Ukraine admits to have lost these territories to Russia in the framework of a peace agreement and accepts its new borders, an entry into NATO would become possible.
How would NATO get involved if Russia successfully took over all of Ukraine?
The expectation and the plan was Ukrainian army would pose little challenge to the Russian forces, Kyiv would fall in a few days and the country in a couple of weeks at the most.
What would follow then is the slow bleeding of Russia as Ukrainians take up arms to endlessly harass Russian occupation forces and domestic collaborators, until Russia runs itself bankrupt trying to occupy a country too large to be effectively held by force of arms or through bribery.
According to Tomaž Vargazon, this was the initial plan, because NATO saw the preparations in Russia and the relative lack of preparations in Ukraine and believed Ukrainian army stood no chance against the Russian onslaught.
What NATO didn’t know was that Russian army was far, far less well prepared than anyone anticipated and that Ukrainian military was better prepared and far better motivated than commonly believed.
After the first week or so NATO was forced to adjust the plans and help Ukraine take Russia head-on and win the war conventionally.