(CNN) — The Ukrainian military is redoubling its efforts to break through thick Russian defenses in its counter-offensive in the south, which has struggled to gain momentum since it was launched in early June.

Ukrainian officials have said little about which new units are committing to the offensive, but the army has clearly added newly minted units equipped with western armor to at least a major segment of the southern front.

The challenges facing the Ukrainians may have less to do with numbers and more to do with capabilities, training and coordination, factors that are critical when an attacking force is faced with such a variety of defenses.

The Ukrainian military fires a small Partyzan multiple rocket launch system at Russian troops near the front line. (Stringer/Reuters)

Geolocated video clips show Western armor such as Bradley Fighting Vehicles have been part of the renewed assault and experienced units have been brought into the fray. But tight operational security on the part of the Ukrainians prevents a full assessment of what is being done to restart the counteroffensive, and where.

There is still debate about the size of the additional effort.

George Barros of the Institute for the Study of War, a Washington-based group, told CNN: “We hadn’t seen any evidence of a battalion-level attack and certainly no brigade-level attack. If the Ukrainians are actually sending in full battalions and brigades now as reported, that would mark a clear new phase of the Ukrainian counteroffensive.”

A Ukrainian brigade has approximately 3,000 soldiers.

mines and more mines
For weeks, Ukrainian forces have struggled to break through the Russian lines due to layers of defense: tank traps, other obstacles and dense minefields. According to some Ukrainian accounts, they have resorted to using small groups of military engineers working in forested areas to clear their way through or evade these minefields.

But sailing them will not break the back of the Russian defenses. Satellite images show multiple layers of Russian fortifications, sometimes 20 kilometers deep: one breach and another await.

Despite rushed training, some of it in Western Europe, Ukrainian forces appear to be struggling to carry out combined arms operations – the use of multiple different assets to suppress and degrade Russian defenses both in the air and on the ground.

“Russian attack helicopters and fighter-bombers are exploiting weaknesses in Ukraine’s air defenses, allowing the Russians to attack Ukrainian ground forces. Carrying out a mechanized penetration of this magnitude while the adversary has air superiority is extremely difficult,” says Barros at the ISW.

“Operations are more sequential than synchronized,” says analyst Franz-Stefan Gady after a visit to the front and extensive talks with the Ukrainian military.

“Ukraine will have to better synchronize and adapt current tactics, without which the western team will not prove tactically decisive in the long term. This is happening, but it’s a slow work in progress.”

In addition, Gady says, the Ukrainian troops he spoke to “are very aware that lack of progress is often more due to use of force, poor tactics, lack of (between) unit coordination, red tape/infighting , Soviet-style thinking, etc.”

A Ukrainian soldier inspects a former position of Russian troops. (Stringer/Reuters)

He says that makes Ukrainians more vulnerable as they try to move forward, and there is some evidence of that in the few videos that have surfaced on social media.

“It’s not just about equipment. There is simply no systematic separation from the Russian defensive system that I can observe,” Gady tweeted. “Weakening Russian defenses to a degree that allows maneuver,” which will include the use of cluster munitions, is a critical task in the coming weeks.
The commitment of new units this week seems to have allowed the Ukrainians to make modest advances south of the city of Orikhiv, approaching the important Russian center of Tokmak, about 20 kilometers south of the current front line.

There are other modest successes further east, but the few front-line accounts that have emerged speak of relentless Russian air and artillery attacks.

Kostyantyn Denysov, a member of the Freedom Legion, said the fighting was relentless.

“In a word, it’s hell,” he told RFE/Radio Liberty this week. “There are small arms battles all along the line of contact, counter-battery fighting.”

“Your helicopters are flying here in pairs.