Tank Leader is a series of games on tactical (platoon/company level) warfare in WWII. The game is heavy on Command, Control, Communications and Intelligence modeling and yet is not any more complex than many other common and popular tactical level games such as Panzer Leader or Panzergrenadier. The key to the game rules are the formations, which are activated by playing command cards. The games do NOT play like Panzerblitz, Panzer Leader, etc. For one thing, the rules are overall a better "simulation" and they are also much better written. For a fuller description of the games see my review
The games were published in the late 1980s by West End Games. Though still in business, West End Games no longer supports these games (or any of the other wargames they published).
Personally, I feel that these games are the best on the scale and topic that I have played. The three difficulties with these games are a) the scenarios are not known for being balanced, b) a lack of players -- few people have a copy or even know of them, and c) solitaire play is almost impossible using the C3I concepts that are the heart of the game.
Tank Leader Consolidated Updates (Word Doc, PDF) represents a consolidation of the rule changes between versions. It also contains my personal notes on the game in separate sections regarding mostly scenario balance plus a few minor rule clarification suggestions. Please check it out.
Tank Leader House Rules (Word Doc, PDF) represents modifications to the rules to suit my own taste. Season to your own tastes, of course.