Iran's Flag

[Marcello]

Well, I have not reaserched Iran extensively (not yet at any rate) but I agree on the not 100% US hardware. I tend to think that for the tanks they might have stayed british and gone for the Challenger 2. I have also my doubts about aquiring used Leopard 2, it would have been much simpler keeping the existing Challenger 1 running.

"Integrated defense with top-notch Patriots and assorted radars I'd say at first."

I should note that in real life they also purchased some soviet stuff, like ZSU-23-4. Given that the US cannot offer much of anything below the area level (basically a bunch of Stinger armed platforms) I think that purchasing some russian air defense systems in the 90's might have been an attractive option (although I should review what are the european offers in this sector to be sure).

[PlasmaKrab]

Not that sure about the Challenger 2 for a lot of reasons. First thing, would it have existed at all? In the first place the Chally 1 was to be used only by Iran, and was taken over by the British Army after the revolution. Had they been accepted by the first customer, what would have been the main tank of the British forces?
Also, it sounds like the early Challenger 1 was plagued by teething problems. How would these have turned out,were the tanks in service half a world away in a not-so-important country? Would the after-market service have been as good as for tanks in Britain? Considering all that, would Iranian tankers keep a fond recollection of British tanks? Good enough to purchase the next one? Upgrading the Challys once purchased goes without saying, but surplus Leo2s (just a thought) would be available soon enough for cheap and give NATO compatibility and upgrade potential.

Thinking about it, I'd say look at the Turkish army and defence industry right now, and apply nearly the same to Iran. Up to the revolution they still had lots of less-than-excellent equipment still running (large army, mind you) which would bear interesting upgrades. Even the AIFV would be a good candidate for the next APC/IFV.

Apparently the JCSS file confirms ZSUs in Iran from the 70s onwards. Given the JCSS also cites SA-6s from the same period, I'd say this is a nice commercial fallout of the 1973 Arab-Israeli war.
As you said, there wasn't much of a Western offer on systems of this level back then anyway. There isn't much still, but in the 80s, how about a nice batch of Chieftain-Marksman SPs?
Other than that, there are a couple of European SAM series that could be of interest, like the Roland, Crotale or Aspide.
There were also a number of Rapier SAMs in service, which could have been upgrade, including to SP Rapiers. I've once seen a pic of a purported domestic SP-Rapier fix on parade, dunno how useable and widespread it could be. SA-15s might be part of the answer...

Thinking about F-15s, there would be a large number of F-4s from the 60s to replace as well, so why not?

[Marcello]

"Had they been accepted by the first customer, what would have been the main tank of the British forces?"

Dunno. From what I know the Challenger seemed to be in the right spot at the right time. The MBT-80 was going nowhere by 1979 and the Abrams was deemed too fuel thirsty by the british army when it appeared. So basically I think that the only alternative to jumping on the
Shir-2/Challenger bandwagon was going for the
Leopard 2. From a practical point of view it would have been better but politically how would have it gone?
The problem with the surplus Leopard 2 is that they are going to replace old stuff, like M60s or Cold war era export soviet tanks, bringing a substantial qualitative improvement and standardization for NATO armies. If you are already sitting on a thousands of Challenger you would not want used and logistically different tanks which are, give or take, in the same quality range. You would want a new tank, which would be used initially to supplement the Challenger and replacing whatever obsolete old junk was left.
The only reason to buy surplus Leos would be increasing the numbers on the cheap, but would that be necessary?

[Marcello]

As I see the alternative would be:
1) Ordering a Challenger 2 lookalike, regardless of whether the british Army is on it or not;
2)Buying new Leopard 2;
3)Buying something else like Leclerc or Abrams or whatever.

Option two might be the best but would the germans sell to the Shah?

[PlasmaKrab]

There are two things that may make more tanks necessary past the Challenger era: 1000 tanks may be overambitious as an order, leading to numbers being cut down at some point, and 1000 are probably not going to be enough for the whole army.
Bear in mind that to this day, the IRIA is reported to number something between 350 000 and 500 000 active personal (Pasdaran included), as opposed to probably nearly 1 million in the 70s (350 000 left with 65% desertion rate reported in 1979, grain of salt not included). Even with these figures, reports give between 1600 and 1700 tanks in current service.

I don't know how many tank units were in active service before the revolution, but with such a force, I'd say 1000 tanks is only enough for maybe the best half of the armored units. Like in many countries, rear-echelon units, mech divisions and the like would go on running with older material for some time. And it's this material that would stand replacement or upgrade in the 90s-2000s.

I agree that the British Army would certainly go for the Challenger as well at some point, but I wouldn't call Iran buying a full batch of Challenger-2s later on 100% certain.
Anyways original Challengers with regular updates would be enough to hold the high ground against any neighbor to this day and for the foreseeable future. So buying a new full batch of Leo2A5/M1A2/Challenger2/Leclerc generation in the 90s may not be top priority. We should probably look or a later replacement like what the Turks look like going for these days (i.e. brand new 4th-generation tank).

Point remains about what to do for the rest of the tank fleet. That's where cheap surplus Leo2s and M-60 upgrade packs come in play. There should be at least 500 60s tanks to replace, upgrade and/or convert. Of these quantities (maybe there were significantly more of them before the war?), about 1/3 is Chieftains, 1/3 M-47/48 and 1/3 M-60s, all pre-revolution.
IDK how many of those would remain in service after the introduction of the Challenger, but there would certainly be some pending upgrade

[Marcello]

The problem with buying Leo2A4 is that while it may be good in the short term you are going to end up with a block obsolescence issue in the long run to deal with, as both would have roughly the same age and tech level.

"That's where cheap surplus Leo2s and M-60 upgrade packs come in play. There should be at least 500 60s tanks to replace, upgrade and/or convert."

For modernization purposes the focus would rather be on the 900-1000 (or whatever, sources seems to differ ) or so Chieftain tanks in service, rather than the M60. I would guess some upgrade, perhaps locally made, to bring them to standars comparable to those of late marks of Chieftain. Then some thought could be given to the M60. M48/47 would be definitively junked. I would say 1000 Challenger, which would still account for a reduction from the original order which was for 1200 Shir 2 IIRC, the 900 or so upgraded Chieftain, say a couple of hundreds of
Chally 2 or whatever and some M60. That is nothing to laugh at. The total armed forces strenght was 500.000 by 1977 IIRC but I cannot cross check ATM.

"brand new 4th-generation tank"

Do you mean T-95/140mm gunned western tanks?

[PlasmaKrab]

You're right, there must have been either high attrition during the war or a typo in one of my sources. 1000 Chieftains would be the bulk of the tank force to replace after the inception of the Shir. Upgrading them to Mk11/12 standard or above would be interesting.
Of course, this considered, the whole Patton fleet would be a secondary concern.

What I meant with a 4th generation tank was a brand new post-2000s one. Only working example I can think of is the Korean K2. The Black Eagle is another project but not yet in its final stage. Make the base requirement 120L55 gun or better, high mobility, hunter-killer/autotracker FCS suite with 2nd-generation TI on both sights, active protection... on a newly designed basis. Don't ask for more details, I'm not too good at this generations game. The idea is just to get a newer design than upgraded 70s/80s tanks (M1A2, Leo2A6, Challenger2E...) which would be not much better than whichever upgrade you could lay over the Shir 2.