Colonel
In the US military, a colonel in the Army, Air Force and Marine Corps is equivalent to a captain in the Navy; the insignia for all four positions is a silver eagle (hence the slang term "bird colonel" to distinguish a full colonel from a "light colonel"). American colonels usually command infantry brigades and USMC regiments.
In the British forces, colonels are just below brigadiers. They are not usually field commanders, instead typically serving as staff officers in between field commands at battalion and brigade level. The insignia is two diamond shaped pips (sometimes called "stars") and a crown. The crown has varied in the past with different monarchs.
In the Confederate army during the American Civil War a colonel wore an insgnia of three stars (not to be confused with the three stars in a wreath worn by Confederate generals). The rank insignia of Colonel was worn by General Robert E Lee throughout his service, even after he became overall commander of the Confederate Armies in 1865.