Original SoD Question
 

So in my game, the original Secretary of Defence from the last duly elected President Tanner is still alive.

Would he be able to come back in 1998, after the RUMP Congress and claim the Presidency or is it since a Congress was held, legitimate or not, he loses the line of succession?

Wow! Talk about a rough one!

First hurdle is, was Congress properly elected? Unless it can be proven that they were elected prior to Washington getting nuked or appointed by a properly elected governor to fill an empty seat, then a census most be conducted so that the congressional seats can be properly apportioned and elections held. But as canon has stated, there were 'issue's with the new Congress.

Based on this, SoD can claim to be the next in line of succession, but getting "Congress" to agree could well intensify the Milgov/Civgov fighting.

Actually the one issue with the Twilight Timeline is that frankly the line of succession part of it is completely and totally wrong. First off the Secret Service would have never allowed the Vice President to stay in the White House with an incoming nuke - they would have knocked her out and carried her out if they had to. Second in a time of war there is no way that the third in line to the presidency would have been allowed to be out of touch in any way - especially after the nukes started flying in Europe and Asia.

And third and the biggest of all - as anyone who has seen Battlestar Galactica knows - there is a long line of people who can assume the Presidency - thus there is no way that there would have been no President - it would take a nuclear attack that would have basically killed off 99 percent of the population to get to that point

Two things first I agree with you about the Secret Service, but kind of sort of disagree about the line of succession. In the real world it is only eighteen people long (or 17 right now as one is not a natural born), where as in Battlestar Galactica she was 43rd. We run out of official candidates at 18 if they are all filled, and even though they would not likely let the top 3/4 of them be round the same place I could very easily see lots of them in just a couple locations. Just thinking to a couple of episodes of Madam Secretary that I have seen they have had the President and something like five or six of the Secretaries, if this was to happen at the same time that they were having a joint meeting of the House and Senate the VP would be there and I may be wrong but I do not see either of these being objected to. Taking out these two locations would take out around 10 of the 18 maybe one or two more. Then losing the other six to eight with all the nukes going off would not be that hard to think could happen. But if you do not get them all then I would expect the line to be refilled in very short order.

There were sixteen at the time of the war - but the wording also opened up the possibility of deputies who had been appointed by Congress. Frankly the whole "no one wants to be President" part of the timeline was just way way too convenient a way to break up the US - and considering how CivGov came into being I could see any actual military command structure saying no way am I turning power over to a govt that was stretching being a legal one past the breaking point

While unlikely the events of the game timeline would occur, it's not impossible as CDAT has detailed. It's a case of a series of bad choices and enemy action coupled with fate and luck colluding to screw things up more than usual.

Now, back to the OP. I don't know enough about the US succession requirements to accurately comment, however I do see the SoD either being used as a figurehead to bolster one sides legitimacy over the other, or even a third side forming around them.

The potential for chaos is breathtaking! :D

Let us not forget that the strikes were on a holiday weekend, Congress not in session and probably spending the time with their families back in their constituencies.

OK there were sixteen, it does not matter about the deputies as they are not in the line of succession. When one of those sixteen dies if congress does not confirm their replacement as secretary they are not in the line, even if congress had already confirmed them as the under secretary.

Regardless of the holiday, there was a pretty damn major war on at the time. Those at the top of government weren't likely to be having a lot of time off, and it's quite possible those people would have brought their families closer so they might be able to grab a few hours with them.
Note that in the initial period after nukes were used (July-August) there was a lot of panic and people heading for the hills. Four months later there'd been no escalation and nukes until then had generally stayed tactical, short ranged with limited payloads (except for those in China of course), and within Europe. As indicated in the timeline and Howling Wilderness, a lot of people had forgotten the initial panic and returned to life as usual, so it seems reasonable given the earlier false alarm(s) many would have been slow to take shelter and left it far too late to act effectively.
Because of this, many who should have known better, and had access to relevant intelligence, would have died that otherwise would have been in shelters.

The question here, to me, is more about what would each side do if the SoD was recovered?

Obviously MILGOV would now fall under him, as the military was his to begin with. What would CIVGOV do? Would the military units under CIVGOV switch to follow their SoD?

Is there a claim for Broward to remain President since in their eyes anyway, he was duly elected?

We are leaning towards Broward still claiming the POTUS but losing all military unit support and eventually committing treason and getting arrested.

Hmmm...and the CIA?

It's a tough question.
Not sure they'd lose ALL military support, but if it could be proven the SoD was alive (bearing in mind the difficulties of communication post nuke), there's a high chance many people would fall into line behind the SoD.
Politics would also play a big role, with quite a few I'd imagine unwilling to accept Broward's apparent illegitimacy as it would have massive flow on effects for their own position.
Another similar consideration is how the commanders of the Civgov units may view their own futures. Will they be arrested and tried for treason for supporting Milgov in light of what may be a more legitimate President?
Will there be an assassination attempt on the SoD?
Can enough Supreme Court judges be gathered together to make a proper constitutional ruling? Would that ruling be accepted?

As for the CIA, I don't even want to think about what would happen there!!!

The question makes me think about the movie "By Dawn's Early Light". Where President Martin Landau is trying to convince various government and military officials that he's not dead and is actually the President. Now given the situation you are giving is no where near as dire as that movie but the SOD would have to be able to prove who he was and also more than likely what he was doing between the Thanksgiviing Day massacre and when he reappears as well. Plus theres the constitutional questions surrounding this event that a Supreme Court would have to decide not just the validity of Civgov but also what kind of time limit is there on line of succession if there is one. I don't believe it is actually spelled out. This is a big can of worms you opened and intriguing to think about.

In our campaign I am working on this storyline

The SoD is visiting Panama while the USOUTHCOM is moved to Panama en force.

There his party is attacked by SPETSNAZ supported Colombian FARC forces, and holds SoD McGregor for roughly 2 years while US Forces in Panama conduct a intelligence war to find him.

He is freed roughly 9/2000 and initiates OpOmega through JSC Cummings.

But in our campaign we have a "Morrow-like" catch and have SoD Samuel McGregor and the new Commander of the 7th Army Jonathan Starks, who are brother in laws, work to rebuild the US while fighting Soviet influence in Central and South America.

Among other lines.... :)

Given he's been a prisoner for two years, his place in the succession is gone I would say. Who know's how his experience has effected him, and what sort of brain washing he's undergone.

We thought about that and I am sure CIVGOV would argue that. But I doubt MILGOV would 'punish' him further for suffering at the hands of the enemy for 2 years.

In fact, it rebuilds the militaries morale and helps light a fire under US Forces...

Thanks for mentioning that, since the missile strikes happened on that day I would think that many government officials would be be out of Washington D.C. and other major centers during the attacks. Those in the line of secession would be moved as soon as the launches were detected. I would image that the US would have some one in secure site as a designated survivor?

Do they say somewhere who the major players are CIV or MIL Gov?

Keep in mind there were MANY false alarms prior to the actual attacks. People have become complacent, so it's quite likely they would not have moved with the speed required, or even moved at all. Many may well have written it off as just another time wasting false alarm and nukes would never be used on US soil....
Yeah, people really can be stupid.