Fighting in Ukraine has entered its third month, but Russian forces have still not achieved the minimum goal previously set by President Vladimir Putin, failing to capture any strategic targets other than the Donbass region in

In eastern Ukraine, Russian forces have controlled about 80% of the territory and are aiming to completely dislodge Ukrainian defense units from Lugansk and Donetsk provinces.

This situation causes the battlefield in eastern Ukraine to form two clear front lines, with the natural boundary being the Siverskiy Donets river flowing northwest – southeast, dividing the Donbass region, blocking the advance of both sides.

A Russian pontoon bridge was destroyed near the Bilohorivka residential area in Lugansk province, Ukraine on May 10.

US officials estimate that Russia has deployed about 100 battalion-level combat groups (BTG) in Ukraine, each unit has about 1,000 troops.

However, US officials say the situation may be about to change, after Russian forces repeatedly shelled targets along the Lugansk industrial belt, including the towns of Severodonetsk and Rubizhne.

After weeks of intense shelling, Ukrainian forces abandoned the defensive perimeter in the town of Rubizhne.

The loss of Rubizhne makes the Ukrainian army’s defense line in the city of Severodonetsk more vulnerable.

In that situation, Russian forces could advance in two directions from the north and east, creating a pincer position to block the resistance of Ukrainian military units in Donbass.

But the Russian advance from the north encountered Ukraine’s natural defense line, the Siverskyi Donets River.

To cross the Siverskyi Donets River as quickly as possible, Russian forces mobilized engineers to build a pontoon bridge and send an armored formation to the west bank to surround the Ukrainian army.

Russian tanks cross the Siverskiy Donets river

Russian tanks crossed the Siverskyi Donets River while participating in a special military operation in Ukraine in a video released on April 9.

Images filmed by drones show that Ukrainian artillery has attacked positions of Russian forces building pontoon bridges across the river.

Recently released satellite images show that at least three pontoon bridges across the Siverskyi Donets River were destroyed and Russian forces suffered many losses in their attempts to cross the river.

The river divides the front line in eastern Ukraine

Ukrainian artillery attacked the Russian convoy crossing the Siverskyi Donets River.

Further west, Russian forces are believed to have crossed the Siverskyi Donets River near the town of Lyman, but it is unclear the size of their force and whether they will control the area permanently.

To continue progress in the region, Russian forces need to maintain supplies from across the border.

Ukrainian forces are said to be advancing towards the west bank of the Siverskyi Donets River and retaking control of the town of Staryi Saltiv.

Pontoon bridges and Russian tanks were destroyed in an unsuccessful attempt to cross the Siverskyi Donets River.

Meanwhile, the battlefield situation in southern Ukraine has changed very little.

US intelligence assesses that Russia will not seek to control the entire southern coast of Ukraine, but will instead strengthen the land corridor from the Crimean peninsula to Ukraine’s eastern border area, as well as seek to annex it.

US Intelligence Director Avril Haines commented that both Russia and Ukraine `both believe they can continue to make progress militarily, so we do not see a viable negotiating path forward, at least in the short term.`

Siverskiy Donets River in the Don river system.