Pakistani forget that rest of our forces would be defensive operations. While IBG are cutting Pakistan into 6-8 pieces, IBG will arrived with just after Brahmos and Prithvi missiles on their airbases and other military infrastructure.
Actually, I have my doubts on even the IBGs....not on their existence, but more on their composition and objectives.
The widely held view is that it will be a division sized force (give or take a brigade), armour heavy and designed for independent operations for 72 hours before reinforcement requirement.
I would not be surprised if the IA has been very selective with the information leak.....Somethings appear to be contradictory IMO.
Firstly, for a division sized force to continue high intensity ops for 72 hours, it will require a pretty big integrated logistics capbility...and we are talking of 100s or even 1000s of truckloads. And that is for the ammunition and fuel only. There will be additional requirements for medical equipment, troop supply.It can be executed no doubt, but it would leave a very long tail for a deep cutting formation.
Then we come to the second contradiction. The IBGs will conduct deep penetrating runs into Pak territory, while the other formations begin massing and reinforcing them. Thus you have the massive, very heavy 120,000 strong I, II & XII Strike corps, the most powerful formations in South Asia (atleast). Why would an army commit its most capable assets to reinforcing a far weaker formation.
I am fairly certain those strike corps will not take a stroll to the border and stand guard. If it reaches the border, it will replace/relieve the IBGs in operation. Anything less and its a waste to have them at all.
Thirdly, Why does everybody assume that all IBGs will have the same size and composition or for that matter have different areas of operations? Or why would an IBG be necessarily be a land force?
One could be an Airborne division, formed by integrating the Para (regular) brigade (with substantially uprated firepower) with army aviation attack wing and heliborne troops. Such dense yet light units can quickly attack and occupy mountaineous positions where hostile reinforcement is limited and slow.
Or they could also support another IBG or even a pair of land mobile IBGs in a co-ordinated operation, with the airborne troops choking strategic routes, blocking resupply, giving the land mobile IBGs much more time to achieve their objectives.
Another IBG could be an amphibious assault brigade or even a couple of amphibious brigades tied together.
These might sound like fantasy, but then most doctrines started out as fantasies...
The reason IMO we haven't heard about the composition of IBGs is that there is no fixed composition at all. It is possible that a number of units (brigades, batallions or even divisions) are earmarked for deep penetrating operations, with the IA forming up an IBG as the need and opportunity arises. The recent exercises do tend to indicate that many smaller formations, particularly the independent brigades are being trained to work in close co-ordination with other units, including Army aviation assets.
Of course though, these are just the extrapolations of my hypothesis.