We know a lot. You can see what it is known by a simple search in military/ army reporting websites.
But what we don’t know are more important.
We don’t know what cyber capability they have. That’s a big part of the current time. The enemy’s Cyber capabilities can be really deadly if you don’t know anything of their existence. For example, cyber capabilities could deter all kind of missiles, especially cruise missile type called tomahawk that the US often fires.
The last cruise missiles attack on Syria for the alleged chemical attack, which was mainly cruise missiles prove my point since a large number of missiles lost their target due to cyber defence. There is no reason to do not think that if Syria has them then Iran has them too (that’s why Submarines are more practical).
We don’t know of their exact radar capability. Radar capability, detection system and navigation are the main part of air defence. Not as much the missile that is fired. Some basic surface-to-air missile if supported with advanced radar system can down the most advanced stealth planes/ drones.
We don’t know enough of their underground missiles silos and sites. We know some of them but not all of them. That’s quite bad. Because if there are a lot more than it was expected, they can overwhelm their opponent.
We also don’t know all types of their ballistic missiles. They might have a couple of undeclared class of missiles with a certain strategic capability that they preferred to keep a low profile.
These uncertainties all make the US worry more about losing some of their best military equipment. The US cannot afford of losing some of their best and scary military equipment that they show to the world to Iran. It’s not really about the price but the superpower posture that would be damaged. For the US maintaining that common belief of being untouchable is really important. It’s a credibility that they have built over years with so much investment.
Russian and the Chinese know this too. Even though they both don’t want that the US attacks Iran but they see some opportunities, for example, if Russian knew that an attack on Iran was imminent, they would do anything in their power so that Iran would down one F35 or sink a Carrier. They will get two things If one F35 was downed; one is to show the world how weak the US has become (something that Russian have long campaigned about, especially against F35), and two is to get access to the remaining of that downed plane to know some of the technology.
The US advance and expensive military equipment have actually made it hold back and fearful of engaging in some conflicts in the fear of getting a hit. For Iran, any damage to the US army is a BIG win. For the US, not so much.
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