Ukraine's unending demand for artillery shells to fight Russia is tapping out critical Western ammo stockpiles, which officials say are almost empty

• The artillery-intensive war in Ukraine is drying up Western ammunition stockpiles.
• A senior NATO military official warned that supplies are now at "the bottom of the barrel."
• Ukraine has begun negotiating contracts to build out its own weapons production. 

NATO's most senior military official warned that the West's ammunition warehouses providing help to Ukraine in its war against Russia are almost empty.