Here's how it works in the IDF's Armored Corps, as far as I know. It's different from the other land forces, mainly infantry, in size as well as grouping.
A tank crew of three (Gunner, Loader, Driver) is commanded by a Commander by the rank of Sgt. or Staff Sgt.
A tank Company of three tanks is is commanded by a 2nd Lt., or rarely by an Lt., with a Staff Sgt. XO.
A tank Platoon of eleven tanks, three Companies, CO and XO tank, is (usually) commanded by a Captain, with a Lt. XO.
A tank Battalion of three Platoons, two operational and one training Platoon, as well as a HQ Platoon, is commanded by a Lt. Col., with a Major XO.
A tank Brigade of three Battalions, plus all HQ, Logistics, Intel and all other associated forces is commanded by a Col., with a Lt. Col. XO.
Brigadier and Major Generals command the Corps', the regional commands, and the branches, i.e., air land and sea.
Lieutenant General (here's only one), is the Head of the General Staff, or Ramatka"l, currently Lt. Gen. Dan Halutz.
The interesting thing is that once you become a Colonel, you go through an Armor Course, which is an abbreviated version of Tank Commanders course and Tank Officer course, in order to ease the understanding and leadership in time of war. Therefore, every Colonel or above in the army, is not only qualified to command an armor Brigade, but is also allowed to wear the Tanker's pin on his uniform.
