I am Brazillian but been following a lot of the events in Europe for a while.

Something a lot people miss, is why Russia is doing what they are doing, many assume they just want to conquer Ukraine "just because", or that it is a purely cultural issue, or that it is Putin personal design.

The major point of contention here is that USA and allies (including NATO and the non-NATO members of Five Eyes) have proven themselves to be very aggressive, there are repeated claims that NATO is defensive, yet a lot of the wars in the past 25 years were started by USA or allies in first place.

So first thing is, yes, Russia has reason to fear USA.

The other problem here is strategic and geographic: Russia border is enormous and in the middle of plains, driving across the border with tanks and reaching Moscow and other major population centers right now is something trivial to do, Russia still didn't recovered properly from WW2 and don't have the manpower to defend such huge border from a land invasion.

When Putin says he is defending Russia survival, he is speaking that literally, Russia border is a major vulnerability.

There are basically three "good" solutions for this problem:

1. Have NATO disbanded or made much smaller. Or join NATO in first place. It is obvious this won't happen and Russia doesn't have the means to make it happen.

2. Conquer surrounding countries until they reach the mountains, that are easier to defend. This of course would result in massive negative repercussions, also a lot of countries that Russia would need to conquer for this joined NATO.

3. Convince somehow the countries between Russia and the mountains, to be neutral and not accept NATO inside them. This way if NATO decided to invade Russia by land, there would be time to mount defenses.

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Russia was basically attempting to do the solution 3 using diplomacy. USA did their best to prevent that, because it would be a victory for Russia and a clear loss from USA point of view. Russia then decided that the option left was force option 3. Attack Ukraine and force them to be neutral.

It ALMOST worked, but the peace talks in march ended being cancelled by the Ukranian side.

So plan became a mix of 2 and 3, conquer some parts of Ukraine and keep trying to convince some "Neutrality" peace.

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The problem now of trying to help Ukraine win, for example by giving them tanks as you suggested, is that option 3 would be gone, and Russia would see themselves forced to use option 2. Russia not declaring war and using "special operation" is meaningful, they are STILL trying to do things semi-diplomatically, but as soon it becomes clear this is impossible, things will be very ugly.

Also Russia has a time limit here, their population is still declining for various reasons (including a cycle where each generation that is descendants of WW2 adults are smaller than the others, Russia demography graph look "wavy" because of this). They must solve the problem of the massive hard to defend border with NATO "now", thus they will get more and more desperate, the next generations will be too small population-wise to defend that border effectively.

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If NATO never had expanded right up the border with Russia, all this would probably been avoided. Yes I know people in the countries that border Russia that joined NATO are happy with NATO and wanted to join, but this doesn't change the fact that NATO members been attacking other countries left and right, and Russia thus has all the right to be terrified of NATO on their giant flat plains border.

Still, NATO did. So what is left now? Ideally NATO should pull back with the condition Russia pull back too, but I think the chance of this happening is close to zero.

What will most likely happen is Russia will keep trying to secure their border by any mean necessary. For NATO this is in a sense a golden opportunity, it means they can keep Russia busy there and grinding themselves to dust as they try to get defensible borders.

But for me that is in Brazil, and I am not pro-Russia, neither pro-USA, I think this is extremely dangerous, because eventually there might be a situation, where the only way for Russia to be safe, is if they turn the the area between their border and the mountains into a wasteland hard to cross, and decide to bomb the shit out of the people there until all that is left is craters and rubble that can be used for defensive purposes.

I see Ukranians having only these paths:

1. Somehow, winning the war without getting bombed to oblivion. (I think the chance of this working is minuscle and not worth attempting for real).

2. Fighting to win and get utterly annihilated eventually, with Russia making sure the country becomes a barrier between NATO and Moscow (unless Russia conquers all of Ukraine first).

3. Cutting their losses, giving Russia some territory that moves the border away from Moscow, and pledging to not help NATO invade Russia in the future.

EDIT: forgot option 4 here, because it is unthinkable, but could happen: Ukraine attempts to win the war because it convinced other countries to actually help them beat Russia, for example with actual boots on the ground... but this would turn into WW3, in this scenario everyone loses.