Reports have emerged detailing Russia’s significant military buildup along the border of Kharkiv, Ukraine, raising alarms about a potential new offensive aimed at capturing the city.

According to The US Sun and The Irish Sun, Russia has amassed a force of approximately 50,000 troops, signaling preparations for a summer assault on what has been dubbed Ukraine’s “fortress city.”

This escalation comes amid warnings from military analysts that Russian President Vladimir Putin may have a critical “four-month window” to achieve a breakthrough in the ongoing conflict before his military resources face significant constraints.

Kharkiv, Ukraine’s second-largest city, has been a symbol of resistance since the onset of Russia’s invasion in February 2022.

Located near the Russian border, it withstood intense fighting early in the war, earning its reputation as a “fortress city” due to its robust defense against Russian advances.

The Ukrainian military reported in April 2025 that Russia was gathering forces for a renewed assault on Kharkiv, a move confirmed by President Volodymyr Zelensky, who noted Moscow’s efforts to gain ground in both Kharkiv and the nearby Sumy region in northeastern Ukraine.

Andrii Pomahaibus, chief of staff of Ukraine’s 13th National Guard Khartiia Brigade, stated, “The enemy is trying to pull its personnel closer to the line of combat contact and conduct at least some assault actions.”

This buildup follows Russia’s recent success in pushing Ukrainian forces out of the Kursk region, which Kyiv had briefly captured in 2024, indicating a shift in focus toward reclaiming strategic territories.

Military analysts cited in The Sun suggest that Putin is operating within a limited timeframe to capitalize on Russia’s current military capacity.

Professor Michael Clarke emphasized that Russia faces a “four-month window” before its reserves of legacy Soviet equipment, including tanks, infantry fighting vehicles, and artillery, begin to dwindle significantly.

By mid-autumn 2025, Russia’s ability to replace losses may rely solely on new production, which could be insufficient to sustain prolonged operations.

Dr. Jack Watling, a military expert from the RUSI thinktank, noted that Russia is likely to pursue a “soft launch” offensive, characterized by a steady increase in assaults across a broader area rather than a rapid, large-scale mechanized push, due to limitations in force quality.

This strategic urgency is compounded by Russia’s recent intensification of air attacks.

On May 25, 2025, Putin launched what was described as the largest air assault of the war, deploying 367 missiles and drones, including 69 ballistic and cruise missiles and 298 drones, many of which were Iranian-designed Shahed models.

Ukrainian air defenses managed to intercept a portion of these, but the barrage underscored Russia’s intent to overwhelm Ukraine’s defenses as part of its broader offensive strategy.