Yea I will search “low yield”...
Why then are we only putting them on subs now?
We are putting them on subs because the selected warhead, the W76, is only used in SLBM's. It was a really cheap way of adding this “escalate to deescalate” doctrine. It also keeps our tactical nukes off the "battlefield" where they are at risk of capture, off of aircraft that could be shot down, and keeps the firing chain at the Commander in Chief level. Sure, a sub could be hunted, but that same sub already carries 2 dozen Trident missiles, so you are just changing the mission of a couple of those.