This is forcing me to think back to the mid-60s when I was in HQ 4 CIBG, although about 15-17 years ago I was interviewed by DHH about this issue, or at least nuclear fire planning and release procedures.
The Canadian brigade group, while along with its supporting organization, Canadian Base Units Europe, formed an independent formation titled Canadian Army National Force Europe (CANFE) commanded by a brigadier who also commanded 4 CIBG. The Honest John battery, 1 SSM Bty RCA, was part of the brigade group. For tactical purposes the Canadian Government had allotted CANFE to Northern Army Group commanded by a British General, who in turn gave us to 1 (BR) Corps. For tactical purposes, we were part of 2 (BR) Div along with 6 and 12 Brigades.
Both artillery units - a RCHA regiment and 1 SSM Bty - operated as part of the divisional artillery and were based in Fort Prince of Wales (Fort POW.) There was another artillery unit in Fort POW, the 69th USA Missile Detachment (69 Msl Det,) which was the custodial unit for 1 SSM and 50 Missile Regiment, RA (50 Msl Regt,) the British nuclear delivery unit in 2 Div. In the field 1 SSM supported 4 CIBG exclusively and we also got an 8-in battery from 50 Msl Regt. For an operation the commander 4 CIBG would get a planning allocation of nuclear warheads - not very many, but that's another story - for both the HJ and 8-in.
The commander's appreciation was built around the use of these weapons and a major obstacle such as the Weser River and/or a minefield. The defensive layout was based on selecting nuclear killing zones and a number of combat team battle positions to be occupied to support whichever killing zone the enemy's advance appeared to be headed towards. I won't bore you with the HJ battle procedure but the battery selected a number of launcher positions from which to shoot depending upon whichever killing zone and nuclear yield was selected.
The President of the United States controlled the warheads and 69 Msl Det held the warheads that might be authorized for 1 SSM and 50 Msl Regt. When and if the President released the nukes, authority was granted to SACEUR, who in turn could authorize the Comd NORTHAG to use the nukes allotted to him. He could pass authority down to his four corps commanders, one each British, Belgian, Dutch and German. The Corps Commander, I think, retained authority, but as the situation warranted the Comd 4 CIBG could issue orders to the CO 1 SSM to prepare to fire a rocket fitted with a certain yield of warhead. He also would send a request up the chain of command to division, where the commander could either support or refuse the request, If refused, the SSM Bty stood down. If supported, the battle procedure continued. If the Corps Commander refused the request, same same. If he supported it, approval came down the chain of command and, on a separate net, the 69th was directed to arm and release the warhead to 1 SSM.
At HQ 4 CIBG the executive order was issued to 1 SSM and a nuclear strike warning was transmitted on the brigade command net. When the launcher actually fired the rocket, this was reported to brigade HQ and a "dazzle" warning with a TOT was issued to alert the troops to don eye protection, take cover, face away, etc.
We don't need, I think, to get into post-strike counter-attacks and the rest, but I hope this helps. As I said, it was a long time ago. The account is generally correct but may have minor errors in detail.
Modify to add: I think the nuclear request/approval stuff went up and down the gunner net or a special gunner nuclear net using a system of One Time Pads to enconde/decode the message.
