Portable Nukes

1) Gravitic tech may make getting the required masses for a reaction
lower possible.

2) PA or Infantry Walkers (Heavy Gears) could easily deploy this in
single or few shot capacities and probably withstand the rads at some
distance from the blast (no direct primary or secondary area mind you,
just the further out rads).

3) Warheads could get smaller. If we're talking about .01 ktons we're
talking about 10 tons which is 10,000 kg. Which is about 20,000 lbs
which is like about the capacity of a flight of small attack craft.
Gross, but not world wrecking. But awful news for a lander. Something
tells me THADs and such would use larger versions of this.

4) As for escalation : They're invading your planet. They've already
taken out most of your orbital net and ortilleried you to soften you up.
It doesn't get much worse. Get the nukes out. You have little to lose.

5) As for not having any working comms: It is not that easy to take out
a redundant comm network. I'm sure a fair sized planet would have the
commsats you'd kill, but they'd have stealthed powered-down redundant
backups you'd never find. Even when they came up, you'd be lucky. You
know how hard it is to find a stealthed satellite? Pretty darn hard.
They aren't that big, they don't mass much, with low power output and
stealth you'd have a real time with them.... And you have buried fiber
landlines which are hard to cut. And ULF. And etc. etc.  If you have
Meson based comms, you cannot disable it. (Of course, then you should
have meson guns too....)

6) As it relates to landings:
You plan to land where the enemy isn't. You cover the contingency you
will be wrong. Thus you arm your landers and armour them. And yes, I
think you do NOT let Marines drive them for good reasons. I'm pretty
certain Marines possess three useful military skills: Marching,
Shooting, and Dying Slowly. (Of course, Marine Air Corps, etc. have some
more technical MOS skills). They shouldn't be operating heavy machinery.
Get them down on the ground, they'll do what they do and sieze you a
spacehead. (is that the 2185 version of an airhead?).
You'd have ortillery if things got hot or if you were "assault landing"
(ortillerying otherwise might be a giveaway). You have orbital split-out
to make it hard to know where your forces are going (equivalent to OTH).
But the enemy has still-hidden spysats... you can't get them all. And
they have guys on the ground with fiberphones and binocs. You won't get
that much time. And if they are an inhabited world, they have missile
batteries and guns buried under tons of rock that you couldn't hope to
hurt until they expose themselves to kill your first wave. So.....
expect a landing against an inhabitted world (even if you have space
superiority) to be a painful process. Plan to minimize, but account for
the Murphy's out there. They'll get you every time.