DNIPRO, Ukraine — Intense fighting raged in southeastern Ukraine this week as Kyiv continued a major push to reclaim territory with a fresh injection of Western-trained and equipped troops but no sign yet of a major breakthrough.

Russia's main defensive line — a phalanx of trenches, tripwires and anti-personnel and anti-armor mines — remains ahead of Ukrainian forces and their objective to drive south and sever Russia's land bridge to Crimea, a key military supply route.

Ukrainian troops have begun to make incremental gains toward that line after swapping out an approach that involved small movements of troops on foot for a larger influx of forces from Ukraine's 10th Corps reserves using tanks and armored vehicles.

"It's monotonous hard work, past hundreds or thousands of minefields," said a Ukrainian military official who like others spoke on the condition of anonymity to discuss sensitive battlefield developments. "We look for the enemy's vulnerable spots and move forward — little by little."

Fierce fighting continues around the village of Robotyne — an area previously held by Russian forces that is less than 11/2 miles from the Kremlin's main defensive line. By several accounts, the battle there presents Ukraine's closest and most feasible path for breaking through the Russian line, with officials characterizing it as having major "strategic value."

The decision to dedicate a substantial amount of reserves to the battle represents the latest improvisation in Ukraine's nearly two-month-old counteroffensive — made possible by the West's investments of tens of billions of dollars in tanks, artillery, armored vehicles, long-range missile systems and other equipment aimed at shifting the balance of power in Ukraine's favor.

The initial phase of the fighting in early June saw forces from Ukraine's 9th Corps using a range of newly acquired Western equipment but incurring losses and making little progress in the face of well-prepared Russian defenses, especially minefields.

The next phase relied on dismounted infantry seeking to exploit Ukraine's asymmetrical fighting methods but also failed to make significant inroads. Instead of waiting to deploy a large portion of 10th Corps reserves for when Ukraine arrived at Russia's main defensive line, Kyiv called them in last week resulting in a major uptick in fighting.

"This last week of fighting has been important because they decided to commit their second echelon of forces in a greater way," said Rob Lee, a military analyst with the Foreign Policy Research Institute who just returned from a visit to Ukraine's front lines to analyze the conflict. "It's not yet clear if Russia has suffered enough losses to create the conditions for a breakthrough. We're waiting and seeing at this point."

A second Ukrainian military official described a grinding but gradual push forward hampered by weather that played to the Kremlin's advantage.

"We are trying to establish a permanent foothold in Robotyne and are working through a variety of challenges," the official said. "Weather conditions are ideal for Russian forces using drones to target our artillery."

Russia's effective use of attack helicopters and loitering munitions have also menaced the Ukrainian troops that have managed to penetrate Moscow's initial minefields.

Ukrainians, including President Volodymyr Zelenskyy, have hailed the liberation of smaller territories in other parts of the southeast, including the village of Staromaiorske last week. Drone footage reveals the intense wreckage of the fight for the small settlement, which had a population of 400 people before the large-scale invasion shrank it down to about 10 last week, Ukrainian officials estimate.

A Russian military blogger who writes under the pen name WarGonzo mourned Russia's loss of Staromaiorske, calling it a key Russian outpost on the front line in the southeast.

Ukraine also dislodged entrenched Russian forces in a village near the occupied eastern city of Bakhmut, site of the war's bloodiest battle, the general staff of Ukraine's armed forces said on Wednesday.

Ukraine's relatively better advance around Bakhmut, which Russia seized in May, could be due to Russian forces having had less time to dig trenches and plant mines than they did in long-occupied territories in southern Ukraine, analysts said.

The Pentagon has projected confidence amid criticisms that Ukraine's Western-trained forces are performing worse than their Ukrainian-trained brethren who stunned the world last autumn with major territorial gains around the strategic cities of Kharkiv and Kherson.

"We continue to see their counteroffensive move forward," Brig. Gen. Pat Ryder, the Pentagon's spokesman, said on Tuesday. "This will be a marathon and not a sprint."

The Pentagon remains confident, he said, that Ukraine "will continue to be able to have the means by which to prosecute this campaign."

Russian President Vladimir Putin has insisted that Ukraine's push has not been "successful" and alleged that Kyiv has suffered heavy casualties.

With dozens of miles to go before Ukrainian troops can reach key occupied cities in the Zaporizhzhia region including Melitopol and Berdyansk, Russian forces have stepped up attacks in northeastern Ukraine, including near the city of Kupyansk.

"They have been building up their forces and their equipment and we now see the biggest concentration of forces and equipment since the occupation of that area," Andriy Besedin, the de facto mayor of Kupyansk, said in an interview. "Aside from sowing terror on civilians, their military push has not succeeded."

Though unsuccessful in reoccupying territory in the north, the Russian push may have its own logic, according to Lee, the military analyst. "It's possible that in doing this, it's forcing Ukraine to take away some of the units they can commit to fighting in the south in the hopes of weakening the offensive," he said.

Ukrainian military officials declined to comment on whether Kyiv has surged reinforcements to the north.

The intense fighting along multiple swaths of the front lines has coincided with a deliberate effort by Kyiv and Moscow to sow chaos and fear in the two countries' respective population centers with long-range drone and missile strikes.

The Moscow-City complex, nestled west of the city center and dotted with glittering skyscrapers, was hit repeatedly by drone attacks in recent days. Among them is the IQ-quarter tower, which houses several government ministry offices. In an attack on Sunday, offices of a government ministry appeared to suffer serious damage, according to photographs published on Russian media.

The assault could have been worse, Moscow Mayor Sergey Sobyanin suggested Tuesday, saying Russian air defenses thwarted "several drones" trying to reach the city.

While Ukraine's use of drones has demonstrated an ability to travel hundreds of miles and reach the heart of Russian political power, its strikes have been far less deadly than those by Russia.

On Wednesday, Moscow attacked Ukraine's primary inland port on the Danube River, sending global food prices soaring. The destruction of the buildings at the port interrupted the movement of ships preparing to load shipments of Ukrainian grain. Ukrainian officials said the attack damaged nearly 40,000 tons of grain. Kharkiv and Odessa have also come under attack in recent days.

"Russian terrorists have once again attacked ports, grain, global food security," Zelenskyy said on Telegram.