Western weapons are now in action in the battle for Ukraine. But getting them into operation on the front lines is creating serious headaches for Ukraine’s military.

Ukrainian officials have depicted Western arms as essential in their efforts to turn the tide of the war against Russia, which has in recent months been making grinding territorial gains—and they want more. Until recently, Ukraine has been dependent on heavy weapons built or derived from Soviet-era systems, of which Russia has better equipment in much greater numbers.

More modern and effective Western weapons, particularly long-range artillery pieces, are now in the fight. They are already making a difference, allowing precision Ukrainian strikes on important ammunition dumps, air-defense infrastructure and command centers deep behind the lines that are disrupting the Russian offensive.

But absorbing this new equipment, coming in dribs and drabs from different Western countries, into the Ukrainian army is proving a serious challenge.

“The current approach by which each country donates a battery of guns in a piecemeal way is rapidly turning into a logistical nightmare for Ukrainian forces with each battery requiring a separate training, maintenance and logistics pipeline,” said the Royal United Services Institute, a London defense and security think tank, earlier this month.