PREMIUM: How more than a dozen factories in the UK could be converted to making shells for Ukraine, Britain and beyond

Artillery's reputation as 'king of the battlefield' may have been challenged by the precision and volume of drone strikes in Ukraine, but big guns remain a key force, as shown by the enormous usage of shells in the war with Russia. 

Until recently, low-intensity conflicts had left artillery sidelined, and maintaining large stockpiles of ammunition was less of a priority.

That has now changed with allied nations running down their stocks as they donated shells - especially the 155mm calibre that are the mainstay of the battlefield - to Ukraine.

The conflict in Russia sees Kyiv’s army fire thousands of 155mm rounds a day, with estimates suggesting that the country is consuming millions a year.  

Now allied planners are looking at how to replenish their arsenals, but in a way that is sensible and sustainable. The problem isn’t just outright capacity to make the shells. There’s also the issue of production flexibility since donors to Ukraine will wish to restock and then pause their orders.

Northrop Grumman, the US defence giant best known for building the B-2 stealth bomber, believes it has the answer.