We trained used a 50 foot lanyard (rope) to fire the Howitzer when loaded with a nuclear shell. You dig a fox-hole to protect yourself first. From that fox-hole, you then pull the lanyard and watch the howitzer destroy itself. The nuclear artillery shell goes down-range, and the tube will exit in the opposite direction.
For obvious reasons, you can only fire one nuclear artillery shell per howitzer.
With 6 Howitzers per Field Artillery Battery, that would make the Russians think twice.