The gulf war, apparently. However, that's not the point. If you watch to the end, the officer explains that the cost of one of these slugs is only 25k yet it

The gulf war, apparently. However, that's not the point. If you watch to the end, the officer explains that the cost of one of these slugs is only 25k yet it performs the same role (and more) of a multi-million dollar missile that a ship can only care a handful of. And boy has the US Military fired a lot of missiles.