ANY illusion that the war in Ukraine is winding down soon should be laid to rest. Ukrainian forces have launched cross-border attacks deep into Russian territory, prompting the evacuation of villages in three regions.

Ukrainian troops are also believed to have taken control of a facility of the Russian energy corporation Gazprom.

Ukraine President Volodomyr Zelenskyy hailed the incursions into the "aggressor's territory," saying he wants Russia to feel the consequences of its invasion almost three years ago.

Moscow was caught napping by the Ukrainian offensive. For months, Russian forces appeared to be consolidating its hold in key areas, particularly Kharkiv in northeast Ukraine, following battlefield successes.

Kyiv was on the back foot, as Zelenskyy chided the United States for not delivering on its promises of more military aid and complained about how recruitment for the war had fallen off.

The Ukrainian thrust sent shock waves across the Russian military establishment. "There is no military system in place for guarding the state border, no reserves and no second lines of defense," one retired Russian general lamented. "If the Ukrainian Armed Forces spent two months preparing for this, how did we miss it?"

A political analyst pointed to "a system failure on multiple levels — intelligence, defense and emergency response" on Moscow's part.

Another reason could be that the Russian border is guarded mostly by conscripts and irregular forces, which were easily overwhelmed by battle-hardened Ukrainian troops.

Whatever the reason, it exposes chinks in the Russian war machine that could wear down its capability to sustain its campaign in Ukraine.

It has also made Putin lose face, so expect heads to roll in the Kremlin. That could happen after Putin met with the Russian Security Council last week.

A massive Russian response is expected. Already, several Ukrainian towns have come under heavy artillery fire. In one eastern city, 14 people were killed after an artillery barrage destroyed a supermarket. Tanks and missile launchers are being rushed to the Kursk region to repel the Ukrainian incursion there.

The counterinvasion, however, has lifted the resurging morale in Kyiv. Zelenskyy was already in high spirits in July when the US announced it was sending Ukraine a new, $225 million arms package that includes rocket and missile launchers, and anti-armor systems.

Just before the start of the Ukrainian thrust, Zelenskyy announced the arrival of the F-16 fighter jets he has long coveted for his country's air force. While the F-16s are not expected to see action over Russia, they will help protect Ukrainian skies against enemy planes and missiles.

The downside to the counteroffensive is that the prospects of a protracted war now loom darker than ever.

The conflict has killed or wounded more than 30,000 Ukrainian civilians. Thousands more have fled the country.

It has also disrupted the flow of goods across the world, sending inflation, interest rates, commodity and energy prices soaring.

Peace negotiations have long collapsed despite several efforts to resuscitate them.

Last June, at Zelenskyy's request, several heads of governments met in Switzerland to draw up a "Formula for Peace" for Ukraine. Because Putin was not invited, the summit was doomed from the start.

There are even speculations that the war is entering an even more dangerous phase. Putin had repeatedly warned he would not rule out using nuclear weapons if Russian sovereignty is threatened.

During a news conference in June, the Russian leader reminded us that Russia has a "nuclear doctrine" conceived in 2020. "Look what it says. If someone's actions threaten our sovereignty and territorial integrity, we consider it possible for us to use all means at our disposal. This should not be taken lightly, superficially," he said.

If the Ukrainian counteroffensive gains more ground, Putin might be forced to play the nuclear hand, even if it means using tactical nuclear weapons in Russian territory to drive out the enemy.

The nuclear option may be nothing but a threat for now, but Putin is too inscrutable for anyone to divine how he will react under extreme pressure.

Maximum restraint must be exercised to prevent a nuclear escalation of the Ukraine war. It is too terrifying a scenario to even ponder.