can some of you guys describe some of the ways you like to deal with someone who is sitting in combat base i had some problems with it the last time i trained
If your legs are long enough, the steering wheel sweep make all your combat base are belong to us. 
I like to sit up into him and, A) go across his body with an arm and get my armpit to his shoulder. This sets up either a guillotine, kimura or a hip bump sweep. Or B) go across his body and go under his armpit with my far arm and sweep to the back or mount.
We do one leg x or x guard. Entry is really easy - a 2 on 1 grip makes it even easier.
I'm certainly no expert at it, but Ive been playing around with De La Riva guard for this. Its important to not let them get their butt down onto their heal initially. If They manage to get their knee in and their butt down, I usually start shrimping out and trying to create space in order to establish some kind of open guard.
i like a strong cross grip on their sleeve and feed the delariva in.
so i delariva hook w/ my left leg and cross grip w/ my right hand on his right sleeve. sweep him over...
if he tries to bail and stand, there's that sweet spot where you can ride up and single leg takedown.
One legged x guard, reverse de la riva, instep to shin and wrap your arm around the low side of the knee and get under his base
It really depends on the size of the base. One of the hardest things about combat bases is that many of them have a lot of abatis to route your movement and where you can move there is usually machine guns with interlocking fields of fire so breaching is tough.For bases with a large amount of personel, you really have to cut off supplies going in. From there soften up their fortifications with artillery and mortar fire. If you have the ability to have an airstrike go for it.
DevilDawg - It really depends on the size of the base. One of the hardest things about combat bases is that many of them have a lot of abatis to route your movement and where you can move there is usually machine guns with interlocking fields of fire so breaching is tough.For bases with a large amount of personel, you really have to cut off supplies going in. From there soften up their fortifications with artillery and mortar fire. If you have the ability to have an airstrike go for it.
I see what you did there.
Combat base seems to me a rather old school move. If all the guy on the bottom has and wants is an arm bar and a triangle, it could be a good position (unless the guy on the bottom is Roger and he simply closes his guard anyway and sweeps you:)
In today's world, however, it is not that solid a position. DBass already talked about Marcelo's approach, but it is also a huge opening for anyone working Berimbolo/Terra's Guard, DeLaRiva, shin-to-shin sit up guard, low single, etc.
Personally, I love it when people hang out in combat base. It is WAY easier than when they stay on both knees or stand.
Exactly.
he is sitting,where is he going?