主题：一些纸上谈兵 -- 北纬42度

Getting the supplies to Ukrainian forces is also a challenge. In the lead-up to Russia’s attack on Thursday, Nato allies could deliver equipment by air or land, direct to military depots. But Ukraine’s skies are now dominated by Russian fighter jets, and Nato allies have said they will not provide air cover as that would effectively mean declaring war on Moscow. Many Ukrainian airfields have also been rendered unusable by missile strikes.

As a result, future deliveries will have to move in more covert conveys through contested territory, most likely from Poland which shares a 535km border with Ukraine and has been the main destination for the Nato troops deployed to its eastern flank this year.

On Saturday, there were reports that airborne Russian forces had landed in western Ukraine, potentially complicating deliveries further.

“Nothing has been cut off by the Russian advance,” a senior western intelligence official said. “There’s a broad range of . . . political and military assistance that can still be provided.”

There are some simple guidelines such aid convoys will probably follow, defence sources say. Trucks will need to avoid moving in bumper to bumper convoys and travel at a variable pace so they are harder to track and attack, and carry air defence weapons such as Stinger missiles and multi-barrel machine guns to deter Russian jets.

“The important thing is guard the handovers, get the supplies to the right place and then disperse them. You can’t just deposit in a depot,” said the defence source. “It’s complex but not difficult.”

Such operations become harder if field units are encircled — as may soon happen to Ukrainian troops fighting in the east of the country.