What views are there on supplying weapons in a war?

In light of the conflict between Ukraine and the Russian Federation, a number of countries, including those with significant catholic and Protestant populations (as well as Christians in their respective parliaments) have allowed for the transfer of military aid to Ukraine.* Is there any basis for, or against, aiding others in conflict, whether the combatants are Christian or not? I ask this as I've previously come across the concept of "Just War", but have been struggling to find anything related to the in-direct support of war. *I may use the example of recent conflict, but I'm aware that there are also numerous historical examples of countries with notable Christian populations and Heads of State that supported conflict, but were not directly involved in the conflict by sending soldiers.