system
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human
[Star Wars]What were the different roles of the ARC Troopers vs. the Clone Commandos? What were the differences in training, doctrine, units sizes, tactics, etc?

I know that real-life countries can sometimes have different special forces, but none of the typical kinds of divisions seem to apply to the ARC vs. Commando distinction. I.e. this isn't like a service division (DELTA Force in the US Army vs SEALs in the US Navy) or a role division (Green Berets being unconventional warfare, Rangers being more of a highly elite conventional unit, and Marine Force Recon focusing on intelligence collection).
gpt
So Arc troopers and commandos mainly differ in when they were chosen for their roles, and how they where trained which leads to their different roles and uses on the battlefield.

Arcs are chosen from fully grown clones that show exceptional skill, creativity, and leadership. They get additional training in spec ops work and advanced battle tactics and strategy. However they are generally work with and are in command of regular troopers or small platoons for special missions like the rescue mission of master Peile. They still fall
Under the general army command structure.

Clone commandos on the other hand are for lack of a better term born for their role, they are chosen and bread from the embryo to be commandos. They grow up in groups of 4, and were trained by about a dozen or so bounty hunters hand picked by Jango Fett. Unit cohesion and stealth tactics are their big focus. And each individual in a unit will specialize in a single task. All will be able to do each other’s tasks sufficiently but  the demo experts will be better at setting charges, you tech specialist will be better at splicing and your marksman will be able to make harder shots than the rest. Because of this unit cohesion and fast, stealthy skill set they are deployed on extremely special usually deep penetration missions far behind the front line battlefields, such as to retrieve the body of the Jedi master killed by Savage Opress, or destroy a secret CIS science facility developing a virus specifically designed to target clone troopers’ specific DNA sequences. You will almost never see deployed with regular clone troopers and the outside of the typical chain of command reporting to Jedi master Arligan Zey who headed the special forces division of the grand army.

While an Arc trooper may be able to go toe to toe with a commando and hold their own, a commando is never alone.