Ukraine's forces are facing 'tough battles' and taking losses early in its offensive, but war experts say it has a lot left to hammer Russian lines

• Ukraine's big offensive is underway, and its forces are fighting what Zelenskyy called "very tough battles."
• There are reports of heavy personnel and equipment losses in some sectors.

As Ukraine takes the fight to the Russian army with the start of big offensive operations, Kyiv's forces are facing hard battles and stiff resistance and suffering manpower and equipment losses for limited gains, but experts caution against counting the Ukrainians out yet.

Ukraine's long-awaited counteroffensive is underway and has been unfolding over the course of the week with clear offensive operations in at least three areas of the front lines, the Institute for the Study for War reported in a Thursday night update.

Ukrainian forces gained ground in areas around Bakhmut, a city of limited strategic value that Russia only recently captured at tremendous cost.

Kyiv's troops also made gains in localized counterattacks in the Donetsk Oblast, but operations in the Zaporizhia Oblast, which ISW described as a "limited but still significant attack," appear to have failed to gain ground.

Ukrainian President Volodymyr Zelenskyy said in a Friday address that the armed forces are fighting "very tough battles." Before the counteroffensive, he said that victory would likely come at a cost and that "a large number of soldiers will die."

In some eastern sectors of the front lines, Ukrainian forces have met greater resistance than expected and suffered heavy equipment and personnel losses trying to punch through Russia's defenses, two senior US officials told CNN Thursday.

One official said that the losses were "significant." Russia is likely also taking losses, as this is brutal combat for both sides in this fight, but information is currently limited.

The report noted that mines, in particular, have taken a heavy toll on some of Ukraine's armored vehicles, and video footage and images have already emerged of armor losses, including at least one of the German-made Leopard tanks Ukrainian forces only recently received.

Though it wasn't always clear when Kyiv's offensive would start, Russia, and really anyone even remotely paying attention to the war in Ukraine, has known this was coming for months now, and the Russians have been digging in in preparation for it.

"To shift the offense-defense balance in its favor, Russia has designed one of the largest defensive systems in Europe since World War II," a new Center for Strategic and International Studies report said, noting that the Russian lines in the Zaporizhzhia Oblast are the "most extensively fortified."

Russia has built a complex and layered defense consisting of hundreds of miles of trenches, razor wire, dragon's teeth anti-tank obstacles, and particularly deadly minefields, as well as with infantry, artillery, and various other weapon systems.

Through its counteroffensive operations, Ukraine is confronting these hardened Russian defenses with a force that while experienced is employing new weapons with, in some cases, new tactics. And it's doing it without air support.

Further complicating things is that the Russian military appears to be, as ISW noted in its latest update, responding to Ukrainian operations in a doctrinally sound manner.

Russians sources, the DC-based think tank reported, have indicated that electronic warfare capabilities, rotary-wing air support, and landmines played an important role in repelling Ukraine's advances.

But the offensive is just getting started. As Yevgeny Prigozhin, founder and financier of the paramilitary Wagner Group fighting on behalf of the Kremlin, said Thursday, "the events that are happening now on the front line signal the start of the offensive and Ukraine will intensify its efforts."

At the moment, it's too early to judge the potential outcome of the counteroffensive, experts say, and certainly too early to draw conclusions from the recent losses, such as Western armor.

"Losses are inevitable during any military undertaking. Ukrainian forces will suffer losses, including of both Western and Soviet equipment, during any offensive operations," ISW said.

"Loss of equipment — including Western equipment — early on in the counteroffensive is not an indicator of the future progress of Ukraine's counteroffensive," it said. "It is important not to exaggerate the impact of initial losses of Western or any other equipment, particularly in penetration battles against prepared defensive positions."

As the think tank noted in a previous update, initial counteroffensive operations may be the "most difficult and slowest" because "the penetration phase of a mechanized offensive" tends to be "the most dangerous and costly."

Losses, within certain limits, are to be expected and won't necessarily break an operation, though there is a point where substantial losses for limited gains risk becoming unsustainable, such as Russia's astonishing 100,000 casualties, according to official US estimates, for roughly 870 square kilometers during Russia's winter offensive. Ukraine's not there yet.

ISW reports that what has been seen so far does not "represent the full extent of Ukrainian capabilities in the current counteroffensive."

Ukraine created 12 counteroffensive brigades, nine of which were equipped with Western weaponry, and it "appears to have committed only a portion of the large reserve of forces available for counteroffensive operations," it said.

Kyiv's forces will have to use these carefully though, as well as be prepared to recover and repair busted systems.

"Ukraine is a formidable force," especially with all its new technologies, retired US Army Lt. Gen. Mark Hertling, who previously commanded US forces in Europe, said Friday in a Twitter thread noting the importance of not only training tank crews but also training mechanics, logisticians, and supporters.

"There WILL be damaged (& some destroyed) western equipment on the offensive battlefield," he said in a social media post. "Things break - a lot - in combat."

In the thread, which began with a photo appearing to show a wrecked Ukrainian tank, Hertling expressed optimism for Ukraine's offensive, despite some early setbacks.

"Early 'hiccups' happen, and offensive ops incur more casualties than the defense," he said. "Ukraine will learn, grow [and] prevail in this operation."

It might be a while, possibly months, though before the outcome of the counteroffensive is clear, so it remains to be seen whether Ukraine's efforts to penetrate Russian lines translate into the kind of significant breakthroughs Ukraine needs. As experts have said, Ukraine needs to make progress in the counteroffensive. The stakes are particularly high for Ukraine going forward.