Dividing and recombining units

[agm]

Can someone explain why the option to divide or recombine a unit sometimes is available and sometimes not. Are there specific criteria I need to meet to have that option available.
Playing Scen 15 w/ 1.8001 as Allies. I have a 72-plane fighter group in Townsville that I would like to split. The FG is assigned to SW Pacific and that HQ is in Townsville, along with over 200k in supplies.
On the other side, I have the 25th USA Inf.Div at Pearl Harbor. I divided it up for the Gilberts invasion. I would like to recombine. It is assigned to Central Pacific and CentPac HQ is also at Pearl, along with over 900k in supplies.
Is there some other criteria I need to meet?
Thanks in advance.
Andy

[ckk]

How many have you already divided? and your opponent? There are a finite number of divides for Both sides once that's reached nobodt divide any further. Recombine another of your ubits and see if the other unit can then be divided[;)]
As far as the 25th division, sometimes when they are split one unit will upgrade and you won' be able to reombine until all split units have the same equipment

[acmejeff]

I am having the same problem. Playing the Japanese, stock game, scen 15, version 1.801. At an island base I have four divisions, some of which have the option to divide and some do not. I have very few units that are divided in my game. Since some can and others can't there must be some criteria for a unit to divide outside of support, supplies, and a co-located HQ unit which all four of mine have. Anyone have any ideas of what my problem could be?

[agm]

CKK --
Thank you. Your advice proved absolutely true on the air groups. I combined some bomber groups and was able to divide the fighter groups. I have yet to examine possible equipment differences for the 25th Division but it's been sitting at Pearl for two months so you think that would have been resolved. Again, thanks.

Andy

[michaelm75au]

The reasons that LCU can't combine is mismatch of ugraded devices between sub-units, and the presence of fragments of the units.
Fragments need to be returned to the unit, and upgrades need devices in pool plus more than 2xrequired supply in a nearby base.
 
It is difficult to distinguish between some infantry squads as they have the same name but have different attributes as they upgrade.
 
Michael