Quick questioning, does this sort of explanation ever make it beyond defence? ie: to the political class?Going back to basics, and using Australian doctrine.
First up, tanks don't fight alone. They fight in pairs; although for command and control reasons they won't break down beyond a Tp (4x Tk)
The primary unit of deployment preferred by Army to meet its obligations is a Bde (commanded by BRIG). It's the smallest self-contained element that has a decent duration. Now, the make up of a Bde is task dependent, but you can expect there will be five manoeuvre battlegroups (commanded by LTCOL). That gives you:
1. a screen or guard (two different missions, but the bits out front)
2. three main BG that will provide the bulk of the combat power for defending or attacking
3. a security or reserve BG (two different missions) that provide depth to the Bde holding.
The screen/guard has to be mobile, traditionally the role of the old cavalry Regt. It's going to be heavy on recce, light on infantry. If a screen it'll try and avoid decisive contact, if a guard it'll take a fight or two. Either way, expect at least a Sqn of tanks is needed.
The main BG will probably be infantry triangles (3x sub-units, 2 inf and 1 tk) although they could be square BG (2x inf and 2x tk). Let's reduce flexibility and assume triangles. That's three Sqn of tank.
The final BG will 'generally' have less combat power, but will still need lots of mobility. Traditionally called rear-area security operations, it's also seen as a cavalry / infantry role. Likely also to feature the Bde Comd's reserve. There will be another Sqn of Tk here.
Straight up that's 5 Sqn of tank - at least. It would probably be better to have at least two of those main BG square, so it's more like 7. But.....lets go 5.
14 tanks to a Sqn (three Tp's of 4 + a Sqn HQ) means 70 tanks. This is just the fighting force.
Now, lets assume the Bde has some spares to account for attrition. Rule of thumb is about 10% for the combat vehicles, but lets cut that a bit - tanks are pretty tough. So 5.
You aren't deploying this Bde for 6 months and nothing else. There is a second Bde in Australia spooling up to take over. Now, they don't need a whole bunch of tanks, thanks to simulation and the progressive need to increase training you can get away with less. Let's assume that the Bde HQ can do CPX's or use simulated forces to do their training, and lets assume we don't need more than two BG in the field at any one time. Their tanks can rotate around and we can lean on simulators for individual training. So, 2 Sqn, another 28 tanks.
On top of all this is the need to be generating RAAC forces from scratch, as well as continue soldier and officer training. So the School of Armour needs tanks. Now, they can use simulators a lot, so at any one point they need 2x Tp of tk. That means the LT's can continue ROBC simultaneous with a Subject course for an NCO rank. 8 tanks.
For those keeping track...that's 111 tanks.
A bunch of tanks are going to be in maintenance, upgrades and the whole bunch. Treating the tank like the sophisticated platform it is (something we need to get better at), lets steal a helo base. Tiger plans on about 4 airframes in the Regt being in deeper maintenance or modifications at any one time....so 25% of the fleet. I'm happy to fudge the numbers a little....so lets say 19 - it keeps the maths simple.
So for what we need to do, we need 130 tanks.
"But Takao" I hear you say, "that's a big Bde. Maybe we can go smaller, you know, for political reasons". Removing 2 BG (shudder...) takes 28 tanks away. So we only need 102 now.....
We currently have 59 tanks.
So right now, if the PM orders an effect that comes with the need for a Bde, the Army cannot deliver. We can't meet a specified mission. We can if you cut the two BG (shudder...) and run no reserves (shuddddder.... #PrincipleOfWar) and run no training (*twitching uncontrollably*) and assume at least 95% serviceability (*bzzzrtsatrb*). Want to guess how long that lasts? Want to know how many lives that costs?
This is to do the job. Can a Boxer do some of those tasks? Possibly. It doesn't have the firepower, the protection or the mobility, but at a pinch it may. You'll take more losses though. And remember, Boxer is larger than an M1, so its less sneaky. Yeah it could take AGTM - how many? Is it more than 40? Can a Boxer close on a defended position? Wire, bunkers, the lot? Tracks can....wheels....hmmm
TL;DR: We need 130 to do the job. Right now. So the 59 we have isn't enough, and hence we need more. Right now.
It certainly doesn’t reach the ears of our ‘analytic’ class (or is roundly ignored, if it does…)
