This is something I wrestle with sometimes as an engineering student and I think it does vary from country to country. You’ve got to ask yourself how the world would be different without those companies - whether other less friendly countries would come to prominence and whether the removal of the such a deterrence would make wars more common. But on the other hand, you should think about how those weapons are used and whether it’s ‘right’ like the defence of Ukraine, or more objectionable like some of the more polarising conflicts around the world. It’s a very difficult question but personally I don’t think I would work for a weapons company coz I don’t know how I’d feel about making something that is designed to kill people