(Bloomberg) -- A British-made Challenger 2 main battle tank was destroyed by enemy fire for the first time as Kyiv presses its counteroffensive against Russian troops in the occupied southeast. 

A video of a destroyed tank near Robotyne, a village in the Zaporizhzhia region liberated by Ukrainian forces last month, was posted on social media Monday. A UK defense official who wished not to be named confirmed the tank — a model that Britain has used for almost three decades — was destroyed. It wasn’t clear whether the crew survived.

Ukraine received 14 Challenger 2s this year from the UK, which was the first of Kyiv’s allies to pledge top-flight, modern NATO-standard tanks for the fight against the invasion. Having broken the taboo, which some western governments feared would provoke escalation with Moscow, the British commitment was followed by a German pledge for Leopard 2 tanks, and a US vow to supply Abrams M1s.  

To read more: What Tanks Ukraine Will Get and Why It Wants Them: QuickTake

Challenger 2s are considered one of the world’s most effective and battle-tested tanks, protected by heavy armor and boasting of a very accurate main gun. The only other Challenger 2 lost in battle was destroyed when a UK-manned Challenger 2 inadvertently shot another in Iraq in 2003, according to a UK army report.

After launching the counteroffensive in June, Ukraine’s troops have been engaged in a grinding fight to punch through Russia’s formidable defense network of trenches, bunkers, and anti-tank barriers both in the eastern Donetsk region and to the south with the intention of cutting the Kremlin’s supply line from occupied Crimea.

After weeks of slow progress, Kyiv’s forces breached the first of three main lines of fortifications last month and are now threatening to stage a wider breakthrough. Infantry units advanced beyond anti-tank obstacles in the area south of Robotyne, according to the Institute for the Study of War. 

 Difficult setbacks and the slow pace of the offensive has worried Ukraine’s allies, who say a long fight risks giving Russian President Vladimir Putin the upper hand in a war of attrition.

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