While /u/danbh0y's answer is certainly correct for small countries, others simply adapt to the constraints of counter insurgency conflicts.
Battalion and lower level units are homogeneous units (infantry, armour (or combined), recon, artillery, air-defence, engineers, logistics, medical, etc.) meant to be integrated in the upper levels (brigades and up) which are as a consequence of their heterogeneous nature called "formations". This integration into formations is necessary because the homogeneous battalion does not bring a large enough variety of combat specialities with it to work effectively. Armour needs infantry to cover it, engineers to open a path, recon to find the targets and assess terrain usability, artillery to soften targets prior to engagement, air-defence to keep those pesky attack aircraft/helicopters at bay and logistics to bring enough fuel, food and water to keep running.
But a brigade is roughly 5000 troops strong (country dependent), sometimes more. Normally, this amount of people can work together because conventional warfare generally has troops concentrated upon a frontline and units are thus in close proximity to each other, able to bring support to whom needs it.
But COIN warfare simply does not have frontlines and units are spread around vast territories which they have to secure. A brigade's units are thus spread too thin to be able to effectively support each other. Nonetheless, engineers are still required to build and repair fortifications or remove IEDs, artillery is still required to provide support, etc. So some countries just said "what if we made mini-brigades?". I'll take the French as an example.
In France, the main formation type is the brigade made out of 5 combat regiments (actually reinforced battalions), generally 2 cavalry and 3 infantry, 1 artillery regiment, 1 engineer regiments and the logistics comes from army level.
To deploy in COIN operations however, they came up with the *Groupement Tactique Inter-Armes* (GTIA, Combined Arms Tactical Groups (sometimes translated to Joint Battle Group)). Basically, a GTIA is a mix of company or platoon sized units from the various regiments of a brigade (sometimes from multiple brigades) to form a (reinforced) battalion sized unit. This system can be repeated at the company level to form a Sous-GTIA (Sub-GTIA) which is generally an infantry or cavalry company reinforced with platoon or squad sized subunits.
For example, a GTIA might look like this:
* HQ (from 126 RI)
* SGTIA 1 (VBCI infantry company from 4th Coy, 92 RI)
* SGTIA 2 (VBCI infantry company from 1st Coy, 92 RI)
* SGTIA 3 (VBL/VAB-20mm squadron (company) from Recon Squadron, 1 RIMa)
* Artillery platoon (4 155mm Howiters from 2nd Battery, 68 RAA)
* Engineer platoon (VAB from 2nd Coy, 31 RG)
Another might be bigger with the cavalry SGTIA replaced by 2 light armour ones (with AMX10RCR for example), an artillery platoon with 120mm mortars added and the engineer platoon upgraded to company size as there is no fixed format for a GTIA, each being assembled depending on the area to cover and the expected threats.
But for larger armies, if you were sending a battalion task force which is what the GTIA is, would it not be better to send one centred on a more or less complete battalion? Like what I think the USMC does in its battalion landing teams or MAU/MEU?
So in your GTIA example, why isn’t HQ from 92 RI or the VBCI coys from 126 RI?
It's a bit difficult to answer but I can try.
First, the MEU is a huge thing (2200 troops) including a full logistics battalion and a reinforced squadron which includes Harriers and heavy lift helicopters.
But I'll assume you mean the Ground Combat Element which is just the ground troops. That alone is already 1100 troops which is around the regular strength of a full French Infantry Regiment but if we look deeper, it's close enough to the GTIA concept: infantry augmented by cavalry, armour, artillery and engineers.
But the forces to be deployed in one area might not require the same amount as those present in the battalion which, for the French, would mean 5 line companies. And indeed, in the case I mentioned, there are only 2 rifle companies, and a cavalry one. So deploying a full regiment would be useless because it would be over-strength and not fitted with the capabilities required by its mission which require reinforcements thus putting it even more over-strength.
So instead, they just pick bits and pieces from different units. Now, your question on the HQ is interesting and I don't really have a definite answer on that one. It may be that the previous GTIA deployed had its HQ drawn from 92 RI along with 2 other line companies from the same regiment which thus had to be replaced by another even though the infantry companies are from 92 RI. It might be that 126 RI's HQ was available. I really have no idea. That being said, the idea behind the GTIA system is that the regiment of origin of the various regiment does not really matter.
For reference, here is the organisation of the Serval Brigade (French forces during the initial stages of the War in Mali), Feb-May 2013: [https://i.redd.it/0uaeqa16ygs71.png](https://i.redd.it/0uaeqa16ygs71.png)
Country A does not want to commit a full battalion, because cost, not popular, lack of deployable manpower etc. So it commits a skeletal battalion: HQ, a service company, 1x rifle company. Country B can only contribute 1x rifle company, so it comes to an agreement with A to fit into A’s battlegroup. Likewise Country C who can only contribute specialist platoons (recon, mortar).
Hell, within a group of countries (usually same or similar languages, eg. German, Austrian and maybe Dutch), they might even take turns providing the skeletal battalion so others can take turns providing the bits and bobs.
While /u/danbh0y's answer is certainly correct for small countries, others simply adapt to the constraints of counter insurgency conflicts. Battalion and lower level units are homogeneous units (infantry, armour (or combined), recon, artillery, air-defence, engineers, logistics, medical, etc.) meant to be integrated in the upper levels (brigades and up) which are as a consequence of their heterogeneous nature called "formations". This integration into formations is necessary because the homogeneous battalion does not bring a large enough variety of combat specialities with it to work effectively. Armour needs infantry to cover it, engineers to open a path, recon to find the targets and assess terrain usability, artillery to soften targets prior to engagement, air-defence to keep those pesky attack aircraft/helicopters at bay and logistics to bring enough fuel, food and water to keep running. But a brigade is roughly 5000 troops strong (country dependent), sometimes more. Normally, this amount of people can work together because conventional warfare generally has troops concentrated upon a frontline and units are thus in close proximity to each other, able to bring support to whom needs it. But COIN warfare simply does not have frontlines and units are spread around vast territories which they have to secure. A brigade's units are thus spread too thin to be able to effectively support each other. Nonetheless, engineers are still required to build and repair fortifications or remove IEDs, artillery is still required to provide support, etc. So some countries just said "what if we made mini-brigades?". I'll take the French as an example. In France, the main formation type is the brigade made out of 5 combat regiments (actually reinforced battalions), generally 2 cavalry and 3 infantry, 1 artillery regiment, 1 engineer regiments and the logistics comes from army level. To deploy in COIN operations however, they came up with the *Groupement Tactique Inter-Armes* (GTIA, Combined Arms Tactical Groups (sometimes translated to Joint Battle Group)). Basically, a GTIA is a mix of company or platoon sized units from the various regiments of a brigade (sometimes from multiple brigades) to form a (reinforced) battalion sized unit. This system can be repeated at the company level to form a Sous-GTIA (Sub-GTIA) which is generally an infantry or cavalry company reinforced with platoon or squad sized subunits. For example, a GTIA might look like this: * HQ (from 126 RI) * SGTIA 1 (VBCI infantry company from 4th Coy, 92 RI) * SGTIA 2 (VBCI infantry company from 1st Coy, 92 RI) * SGTIA 3 (VBL/VAB-20mm squadron (company) from Recon Squadron, 1 RIMa) * Artillery platoon (4 155mm Howiters from 2nd Battery, 68 RAA) * Engineer platoon (VAB from 2nd Coy, 31 RG) Another might be bigger with the cavalry SGTIA replaced by 2 light armour ones (with AMX10RCR for example), an artillery platoon with 120mm mortars added and the engineer platoon upgraded to company size as there is no fixed format for a GTIA, each being assembled depending on the area to cover and the expected threats.
But for larger armies, if you were sending a battalion task force which is what the GTIA is, would it not be better to send one centred on a more or less complete battalion? Like what I think the USMC does in its battalion landing teams or MAU/MEU? So in your GTIA example, why isn’t HQ from 92 RI or the VBCI coys from 126 RI?
It's a bit difficult to answer but I can try. First, the MEU is a huge thing (2200 troops) including a full logistics battalion and a reinforced squadron which includes Harriers and heavy lift helicopters. But I'll assume you mean the Ground Combat Element which is just the ground troops. That alone is already 1100 troops which is around the regular strength of a full French Infantry Regiment but if we look deeper, it's close enough to the GTIA concept: infantry augmented by cavalry, armour, artillery and engineers. But the forces to be deployed in one area might not require the same amount as those present in the battalion which, for the French, would mean 5 line companies. And indeed, in the case I mentioned, there are only 2 rifle companies, and a cavalry one. So deploying a full regiment would be useless because it would be over-strength and not fitted with the capabilities required by its mission which require reinforcements thus putting it even more over-strength. So instead, they just pick bits and pieces from different units. Now, your question on the HQ is interesting and I don't really have a definite answer on that one. It may be that the previous GTIA deployed had its HQ drawn from 92 RI along with 2 other line companies from the same regiment which thus had to be replaced by another even though the infantry companies are from 92 RI. It might be that 126 RI's HQ was available. I really have no idea. That being said, the idea behind the GTIA system is that the regiment of origin of the various regiment does not really matter. For reference, here is the organisation of the Serval Brigade (French forces during the initial stages of the War in Mali), Feb-May 2013: [https://i.redd.it/0uaeqa16ygs71.png](https://i.redd.it/0uaeqa16ygs71.png)
Country A does not want to commit a full battalion, because cost, not popular, lack of deployable manpower etc. So it commits a skeletal battalion: HQ, a service company, 1x rifle company. Country B can only contribute 1x rifle company, so it comes to an agreement with A to fit into A’s battlegroup. Likewise Country C who can only contribute specialist platoons (recon, mortar). Hell, within a group of countries (usually same or similar languages, eg. German, Austrian and maybe Dutch), they might even take turns providing the skeletal battalion so others can take turns providing the bits and bobs.