in my opinion this is very straightforward. the people working directly on power, water and materials don’t have any control over how those things are used and often don’t/can’t know what they’re being used for. however, at some point, a decision is made - for example, someone at the company that makes the steel alloy decides to sell it to raytheon - and so whoever made that decision is responsible.

and yes, if you work on a weapon safety system, you are working on an essential part of that weapon and so are responsible for its use