You do realize that if you "reduce" spending you will still have arms companies making weapons and engineers will work for them? I don't think it's that complicated...
You spend a lot on weapons. If you reduce it you will spend less on weapons but you will buy some weapons.
Like imagine you're spending $100 a week on alcohol. You decide it's bad for you and you reduce it. Now you're only spending $30 on alcohol. You're still buying alcohol. You spend less but you still buy it so someone will still make it.
Hope that helps.