There is a major sticking point often overlooked in the ceasefire negotiations between Ukraine and Russia currently being held in Abu Dhabi. This relates to the fact that, as part of any agreement, Kyiv is being asked to give up the entire Donbas region in eastern Ukraine.

If it does so, it will also be giving up the strategic positions that have prevented major advances by the Russian military for many months now. This is the significant line of defensive fortifications across the Donbas, known as the “Donbas line”. It’s Ukraine’s equivalent to the Maginot line of forts which were France’s main line of defence against Germany before the second world war.

The “Anchorage formula” agreed by the US president, Donald Trump, and Russia president, Vladimir Putin, in Alaska late last year calls for Ukrainian forces to abandon the areas of western Donbas they currently hold. Washington is now talking up the idea of establishing a “free economic zone” or “de-militarised zone” which would cover the whole of the Donbas, including those portions currently occupied by Russian forces.

This would mean Ukraine abandoning the Donbas line. The system integrates at least seven distinct defensive layers that any attacking force must penetrate sequentially to achieve effect.

These include minefields, anti-tank ditches, anti-tank obstacles (“dragons’ teeth”), bunkers, trench lines and anti-drone defences. Such obstacles can either physically halt assaulting Russian........

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