How will we know when Ukraine's long-awaited counteroffensive has started? Experts say look for the Western armor.

• For months, Ukrainian officials have signaled that a much-anticipated counteroffensive is imminent.
• Recent Ukrainian counterattacks and limited gains around Bakhmut have caused confusion in the Russian ranks.
• But military experts say Kyiv's use of Western armor will signal the start of a larger offensive.

Russia's war in Ukraine is inching toward the 15-month mark, the front lines are largely static, and questions are swirling about when Kyiv's forces will finally launch their highly anticipated counteroffensive.

When, exactly, this might happen has already stirred confusion within Russia's military ranks, especially as Ukraine makes small territorial gains in the country's eastern region. But military experts say the ultimate signal that a large-scale offensive is underway will be when Kyiv's forces integrate heavy armor provided by the US and its NATO allies into a front-line push.

"The Ukrainian counteroffensive, I think, is going to start with a bang, literally and figuratively," Mark Cancian, a retired US Marine Corps Reserve colonel, told Insider.

For months, Ukraine has signaled that it will carry out a massive counterattack aimed at liberating occupied territory as a follow-up to a successful Ukrainian counteroffensive last summer and early fall. Ukraine's expected counterpunch will come on the heels of what turned out to be a lackluster offensive carried out by Russian forces during the winter.

Moscow's troops failed to make significant territorial advances, despite paying astonishingly high costs in human lives. The fighting is largely a grinding war of attrition along front lines that don't change much day to day. The focus of hostilities has primarily been the war-torn eastern Ukrainian city of Bakhmut.

To help Ukraine prepare for its attack, its Western supporters — like the US and NATO members — have committed mountains of heavy armor. This includes advanced, modern tanks, armored troop carriers, infantry fighting vehicles, and other systems to help beef up Kyiv's arsenal, such as air defense and artillery. The armored vehicles in particular are expected to help Ukraine hit hard and exploit gains quickly with shock, firepower, and mobility.

Although the offensive's operational details remain a tightly guarded secret by Ukrainian officials, they have spoken publicly at times about Ukraine's ambitions and given indications that the military is ready. Ukrainian Defense Minister Oleksii Reznikov said in late April that Kyiv was ready to use the Western arms to hit Russia with an "iron fist."

"As soon as there is God's will, the weather and a decision by commanders, we will do it," Reznikov said. "We are to a high percentage ready." He later backtracked, expressing reservations. Ukrainian President Volodymyr Zelenskyy told European broadcasters last week that his forces still need more time. Not everyone was convinced the Ukrainian leader was sincere though.

The 'real sign' is Western armor

Amid speculation over when Ukraine's counteroffensive will begin, recent territorial gains by Kyiv's troops are already causing confusion within the Russian ranks.

Ukrainian forces signaled last week that they made advances and carried out "effective counterattacks" in front-line areas, including around Bakhmut, where Wagner Group mercenaries have played a key role in Russia's campaign. A Ukrainian battalion even said that it chased Russian soldiers from parts of the city and published footage that appeared to show them fleeing.

Yevgeny Prigozhin, the leader of Wagner, later claimed Ukraine's advances indicated that its counteroffensive was in "full swing" and accused Zelenskyy of lying when he said the country needed more time.

Kyiv's military officials, however, said the advances were only a "positional struggle" and did not mean the start of a broader offensive. And Russia's defense ministry, which regularly pushes disinformation about the war, denied the reports that Ukraine had even achieved any front-line breakthroughs.

Military experts told Insider that Kyiv's gains around Bakhmut are not the start of its counteroffensive, which will actually kick off with the eventual integration of Western tanks and armored vehicles.

"The real sign of the Ukrainian offensive is going to be the commitment of Western armor," Andrew Metrick, a fellow with the defense program at the Washington-based Center for a New American Security, told Insider.

Metrick said that when we see the huge amount of weaponry and heavy armor committed to Ukraine by Western partners, from infantry fighting vehicles and armored combat and reconnaissance vehicles to personnel carriers and tanks, "I think that would be probably the biggest harbinger of that the Ukrainians are serious about undertaking an offensive operation in whatever strategic direction those show up in."

It's unclear exactly how much of this Western armor Ukraine already has in its arsenal, as some training continues and some systems are still in the delivery stage, but NATO Secretary General Jens Stoltenberg said in late April that over 98 percent of the promised combat vehicles had been delivered to Kyiv, including more than 1,550 armored vehicles, 230 tanks, and "vast amounts of ammunition."

"In total we have trained and equipped more than nine new Ukrainian armored brigades, this will put Ukraine in a strong position to continue to retake occupied territory," Stoltenberg said. However, during Zelenskyy's interview with European broadcasters, which was published last week, he said that Ukraine's military still needs additional resources, like armored vehicles, which he said were "arriving in batches."

But as Cancian, a senior adviser with the international security program at the Washington-based Center for Strategic and International Studies, said, these armored brigades, which have been trained and equipped by NATO countries, will give Ukraine the ability to start its counteroffensive "with a bang."

Ukraine is unlikely to just "dribble" these forces into battle. Instead, it is more likely to "unleash" them all at once after a massive preliminary bombardment, Cancian said. Infantry troops could then attack the Russian defensive lines with tank forces breaking through to make deeper gains. "When it happens, I think it's going to be very obvious," he said.

Ukraine won't reveal its offensive right away

The exact timeline for when the counteroffensive will start still remains a mystery, but despite needing more military equipment and hardware, a constant state for Ukraine as it fends off the Russians, Zelenskyy did acknowledge that combat brigades — some trained by NATO — were ready.

"We can go forward, and, I think, be successful" with the equipment that Ukraine already has, Zelenskyy told European broadcasters. "But we'd lose a lot of people. I think that's unacceptable. So we need to wait. We still need a bit more time."

When Ukraine's counteroffensive does finally get underway, it might take some time before Kyiv reveals any specific details to the public.

Cancian said that Ukraine will probably wait several days before making any public statements about its counteroffensive so it doesn't give anything away to the Russians and can keep Moscow guessing about timing and location until it's obvious what's happening.

"If the Ukrainian armed forces had their way, they would try to keep the wraps on this as long as possible," Metrick said. "That's just good operational practice — you want to maximize fog and friction. You want to keep the Russian armed forces guessing as to, is this actually the commitment of their main forces?"

It's unclear if Ukraine has the ability to execute this strategy, but from an official messaging perspective, Kyiv is unlikely to announce when the offensive is unfolding until it's "blatantly obvious" to everyone after a few days, Metrick said.

If Ukraine achieves operational success it can report, that might move forward the timeline for strategic messaging because it could boost national morale, strengthen international cohesion, and degrade Russian optimism.