What are the different levels of generals, i.e., major general,
lieutenant general, brigadier general, etc.? How many types of
generals are there, and what is the rank order?

Hello ouy-ga,

There are four types of generals in the US Army: Brigadier Gneral (1
star), Major General )2 stars), Lieutenant General (3 stars), and
General (4 stars). The five star General of the Army was a rank that
was established in World War II and the last holder of the rank,
General of the Army Omar Bradley, died in 1981. The links below give
you the structure of the ranks as well as the associated insignia.

Best wishes for your explorations.

~ czh ~


http://en.wikipedia.org/wiki/United_States_Army#Rank_Structure
Structure of the U.S. Army
Rank Structure

General officers 
 -- Brigadier General (BG; pay grade O-7)- one star, 
 -- Major General (MG; pay grade O-8)- two stars, 
 -- Lieutenant General (LTG; pay grade O-9)- three stars, 
 -- General (GEN; pay grade O-10) - four stars 
 -- General of the Army - five stars in a pentagon 

http://www.historyguy.com/5-star-military.htm 
Five-Star Generals and Admirals of the United States

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http://en.wikipedia.org/wiki/General
General

In the United States Armed Forces, "General" may mean either any rank
of general officer, or the highest regular rank, which is usually
referred to as full general, or four-star general, if necessary to
identify it specifically. The different ranks of general are
identified by the number of stars worn; a General of the Army wears
five stars, a General four stars, a Lieutenant General three stars, a
Major General two stars, and a Brigadier General one star.

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http://www.fact-index.com/u/un/united_states_army.html
http://www.army.mil/cmh/faq/FAQ-5star.htm
How many U.S. Army five-star generals have there been and who were they? 
Five-Star Generals and Dates of Rank:

General of the Army George C. Marshall: December 16, 1944
General of the Army Douglas MacArthur: December 18, 1944
General of the Army Dwight D. Eisenhower: December 20, 1944
General of the Army Henry H. Arnold: December 21, 1944
(Redesignated General of the Air Force pursuant to Public Law 58, 81st
Congress, approved May 7, 1949):
General of the Army Omar N. Bradley: September 20, 1950 

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http://www.defenselink.mil/specials/insignias/officers.html
The United States Military ? Officer Rank Insignia

Officer ranks in the United States military consist of commissioned
officers and warrant officers. The commissioned ranks are the highest
in the military. These officers hold presidential commissions and are
confirmed at their ranks by the Senate. Army, Air Force and Marine
Corps officers are called company grade officers in the pay grades of
O-1 to O-3, field grade officers in pay grades O-4 to O-6 and general
officers in pay grades O-7 and higher. The equivalent officer
groupings in the Navy are called junior grade, mid-grade and flag.

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http://www.amvets-ny.org/refmil_ior_USA.html 
US Army Insignia of Rank

http://www.military-historians.org/company/journal/five-star/fivestar.htm 
FIVE STAR INSIGNIA
GENERAL OF THE ARMY/ADMIRAL OF THE FLEET

With the death of General of the Army Omar N. Bradley in April of
1981, the five-star rank passed into American history. And it is that
passing which seems to make a brief survey of the five-star insignia
of the General of the Army and the Admiral of the Fleet appropriate.




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us army ranks generals

Excellent, well done! Thanks so much.

Hello ouy-ga,

I'm glad the answer was helpful. Thank you for the generous tip.

~ czh ~