The counterattack began in the last days of August and initially focused on the southern region of Kherson, which was swept away by Russian forces in the early days of the invasion. But just as Moscow was redirecting attention and troops there, Ukraine was launching another highly effective offensive in the northeastern region of Kharkiv.

Faced with the prospect of a large group of its forces being encircled, Moscow ordered a withdrawal of troops from Kharkiv, in a dramatic change in the picture that posed the biggest challenge to the Kremlin since it launched the invasion on February 24.

“The Ukrainian army has taken advantage of the relocation of the bulk of Russian forces to the south and is trying to direct the course of the war, excelling in maneuver and showing great ingenuity,” said Mykola Sunhurovskyi, a Razumkov’s military expert. Center, a Kyiv-based think tank. Ukraine’s quick wins, he added, are “important both for seizing the initiative and boosting morale.”

Ukrainian President Volodymyr Zelenskyy praised the military in a video address on Saturday evening, saying it had reclaimed around 2,000 square kilometers (more than 770 square miles) of territory so far this month. He also taunted Moscow over his withdrawal, saying the Russian military was “showing its best – showing its back” and “it made the right choice to flee”.

Both sides have suffered heavy casualties in Europe’s biggest conflict since World War II. Ukraine’s military leader said last month that nearly 9,000 of the country’s soldiers had been killed in action. And although Moscow hasn’t reported its own casualties since March, Western estimates put the death toll at 25,000, with wounded, captured and deserters bringing total Russian casualties to more than 80,000.

Ukraine sought to mobilize the population to reach an active army of one million, while Russia, on the other hand, continued to rely on a limited contingent of volunteers for fear that a mass mobilization n fuels discontent and disrupts internal stability.

As the war continues, an increasing flow of Western weaponry over the summer is now playing a key role in the counteroffensive, helping Ukraine significantly boost its precision strike capability.

Since the start of the counter-offensive, Ukraine said, its forces have taken over more than 30 settlements in the Kharkiv region.

In the Kherson region, troops sought to drive Russian forces off their feet on the west bank of the Dnieper, a potential vantage point for a deeper push into Ukraine by Moscow.

The city of Kherson, an economic hub at the confluence of the Dnieper and the Black Sea with a pre-war population of around 300,000, was the first major population center to fall during the war.

Russian forces also made inroads into the Zaporizhzhia region further north, where they seized Europe’s largest nuclear power plant. The last of its six reactors was shut down on Sunday after operating in risky “island mode” for several days to generate power for the plant’s crucial cooling systems after one of the power lines was restored.

Moscow installed puppet administrations in the occupied areas, introduced its currency, distributed Russian passports and prepared local plebiscites to pave the way for annexation. But the counter-offensive has derailed those plans, with a senior Moscow-backed official in Kherson saying the vote there must be postponed.

The counterattack followed methodical strikes on Russian infrastructure and supply lines. Ukrainian forces used US-supplied HIMARS multiple rocket launchers to pound the two bridges over the Dnieper, forcing Russian troops in the Kherson region to rely on pontoons which also faced strikes daily.

Last month, a series of explosions also hit airbases and an ammunition depot in Crimea, underscoring the vulnerability of the peninsula annexed by Russia in 2014 and crucial for its operations in the south. Ukrainian authorities initially refrained from claiming responsibility, but the country’s military chief, General Valerii Zaluzhnyy, has in recent days acknowledged that his forces hit them with rockets.

Ukrainian military analyst Oleh Zhdanov said that “Ukraine used the tactic of methodically exhausting the Russian military, weakening it and depriving it of the opportunity to steadily build up its forces.”

Unlike in the south, where Ukraine’s counter-offensive proceeded more slowly on the arid Kherson steppes that left troops vulnerable to Russian artillery, the forests of the Kharkiv region provided natural cover that allowed lightning-fast surprise attacks in multiple directions.

“Speed ​​and surprise became key elements of Ukrainian army action in the Kharkiv region after Russian forces deployed there were relocated to the south,” Zhdanov said.

Michael Kofman, a Russian military expert with the Virginia-based think tank CNA, said the counteroffensive “turned out to be a very significant victory for Ukraine.”

“Russian forces appear to have been scattered and military leadership unprepared despite earlier evidence of Ukraine’s rise,” Kofman wrote. “I think it’s fair to assess that Russia was taken by surprise with few reserves available locally.”

After capturing the town of Balakliia, some 55 kilometers (about 34 miles) southeast of Kharkiv, Ukrainian forces quickly pushed their offensive further east towards Kupiansk, a vital rail hub to support Russian operations In the region.

They claimed control of the strategic city on Saturday, cutting off supply lines for a large group of Russian forces around Izyum to the south. To avoid their complete encirclement, Moscow ordered the hasty retreat, claiming they were moving to concentrate on the nearby Donetsk region.

Zhdanov noted that a successful counteroffensive is key to persuading allies to further increase arms deliveries to Ukraine, which was discussed at a NATO meeting in Germany on Thursday.

“The events in the south and in the Kharkiv region must show the West that the Ukrainian army knows how to handle weapons and must develop its success,” Zhdanov said.

Yuras Karmanau in Kyiv contributed to this report.

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