AMNA NAWAZ: Ukraine and Russia today met for the second time in two weeks to discuss peace, but walked away without any progress towards ending the war.

The fighting is as intense as ever.

And, this weekend, Ukraine launched an unprecedented attack, launching drones deep inside Russia to target Russian bombers.

Nick Schifrin reports.

NICK SCHIFRIN: Today in Turkey, a tense face-off, two foes failing again to end Europe's largest war in 80 years.

And while the war rages, the two sides are as far apart as ever.

Ukraine is demanding a complete cease-fire before formal negotiations, the freedom to join the European Union and NATO, foreign military security guarantees, no military restrictions, and no legal recognition of Russian-occupied territories.

The Russian demands almost exactly opposed, no unconditional cease-fire, a block on Ukraine's joining NATO, the exclusion of all foreign military support in intelligence, caps on the size of Ukraine's military, and the withdrawal of Ukrainian troops from at least four regions of which Russia only controls a portion, as well as international recognition of all occupied Ukrainian territory as Russian.

Ukrainian President Volodymyr Zelenskyy accused Russia of stalling.

VOLODYMYR ZELENSKYY, Ukrainian President (through translator): They said they're ready for a two-to-three-day cease-fire to collect bodies from the battlefield.

I think they're idiots, because the whole point of a cease-fire is to prevent people from being killed in the first place.

I really want our American partners to take strong steps to impose a package of sanctions and to pressure the Russians into a cease-fire.

NICK SCHIFRIN: Russian delegation head Vladimir Medinsky was more matter of fact.

VLADIMIR MEDINSKY, Head of Russian Delegation (through translator): We have handed over our memorandum to the Turkish side, which consists of two parts, first, how to achieve a real long-term peace.

And the second part is what steps should be taken to make a full-fledged cease-fire possible.

NICK SCHIFRIN: The two sides did agree today to exchange the bodies of killed soldiers, 1,000 wounded, ill or young prisoners, and Russia will return more than 300 Ukrainian children kidnapped near the front lines.

But, this weekend, Ukraine reached well beyond those front lines, launching more than 100 drones that had been hidden inside shipping containers and trucked inside Russia to attack Russian bombers.

Ukraine claimed to have destroyed more than 40 bombers on four military bases some thousands of miles from Ukraine's border, the destruction of at least a handful of planes visible from space.

Ukraine said the operation took more than a year-and-a-half to plan, and a senior U.S. defense official confirmed Ukraine provided no advanced warning.

Meanwhile, Russia's strikes have accelerated this weekend.

It launched the largest drone salvo of the war.

One attack killed more than a dozen soldiers, leading to Ukraine's land forces commander, Amna, submitting his resignation.

AMNA NAWAZ: Nick, take us back to that Ukrainian unprecedented attack deep inside Russia.

How significant an attack was that?

NICK SCHIFRIN: So the Ukrainians claimed it was 41 Russian bombers.

Russia only has about 90 of these bombers.

So if Ukraine is telling the truth, then it's a huge portion of Russia's strategic assets in terms of its bombers.

A senior defense official yesterday told reporters that the number is probably inflated, and a separate U.S. official told me that as well.

But, nonetheless, it is a very significant strike.

We have seen multiple aircraft burned out, even from space, as I pointed out.

It shows a lot of planning.

It shows an intelligence capability inside Russia that we did not know Ukraine had, just logistics, trying to get all of those drones, to construct them in Russia, to build some kind of container to conceal them, and then to get close to these four bases.

That shows a level of sophistication that a senior defense official told us yesterday we have not seen Ukraine have.

It also demonstrates, Amna, perhaps that Ukraine still has the capability to do that kind of attack again.

AMNA NAWAZ: So even if the numbers are potentially inflated, could that potentially reduce Russia's ability to carry out strikes against Ukraine?

NICK SCHIFRIN: So, I think part of it does depend on the numbers, the number of bombers that they in fact end up having to have destroyed.

But what this will do, even if the number is lower, it will require the fewer bombers that they have to fly more frequently.

And, therefore, it should reduce the number of sorties that Russia can launch in order to launch these glide bombs, these cruise missiles into Ukraine, which has been absolutely devastating for Ukrainian forces.

So, again, we don't know the full impact, but it's bound to have a negative impact on Russia's ability to launch deep into Ukraine.

AMNA NAWAZ: Aside from Ukraine, these are bombers that fly around the world, right?

They have the purpose of showing off Russia's reach and their nuclear capability.

Does this weaken Russia's global military reach?

NICK SCHIFRIN: I think it's a really important question.

So, when we put it into the context of other Russian losses, think about the lack of bases now in Syria, because Assad has been overthrown.

Think about the Black Sea fleet, which has been a cornerstone of Russia for centuries.

They have lost their ability to have that Black Sea fleet in Western Crimea on the Black Sea.

Think about the percentage of helicopters, of armor, right?

These get into strategic losses for Russia.

And some of the analysts who are looking for this attack, frankly, to be outsized in terms of its impact do believe that these kinds of strategic losses will add up and that, even if Russia doesn't have to necessarily stop attacking Ukraine tonight or next week or next month or even this year perhaps, these things will add up in Putin's mind.

And the hope of these analysts is that the costs of this war simply add up for these strategic losses, rather than the tactical or operational stuff inside Ukraine itself.

AMNA NAWAZ: As you reported, Russia then, of course, launched its largest drone attack over the weekend.

And you saw then, in Istanbul, Moscow is really sticking to its maximalist demands in those negotiations.

Does all of this say to you that they are not yet, Russia is not feeling any kind of military pressure right now?

NICK SCHIFRIN: I think that's the key question, of course, that Ukraine is interested in and Washington is interested.

The evidence is exactly what you just said, that there's nothing on the ground that is forcing Putin to change his calculus, to change his behavior.

If anything, we have seen signs that Russian forces believe that they can keep going, thanks largely to Chinese investments in Russia's defense industrial base.

So this kind of attack individually has no sign that Russia will have to stop any time soon.

And, tonight, in fact, they are warning of a - - quote -- "disproportionate response."

But, nonetheless, some analysts do believe that they are trying to get under Putin's skin, so to speak.

And this kind of attack is just, frankly, almost humiliating.

It's just very public in a way that Ukraine is hoping long term does affect Russia's ability to launch the war.

AMNA NAWAZ: Fascinating reporting.

Nick Schifrin, thank you, as always.

NICK SCHIFRIN: Thank you.