What is the abbreviation for the largest war in which the US forces have fought in?

WWII which is an abbreviation for World War 2.

WWII which is an abbreviation for World War 2.

WWII which is an abbreviation for World War 2.

WWII which is an abbreviation for World War 2.

WWII which is an abbreviation for World War 2.

WWII which is an abbreviation for World War 2.

WWII which is an abbreviation for World War 2.

WWII which is an abbreviation for World War 2.

WWII which is an abbreviation for World War 2.

WWII which is an abbreviation for World War 2.

WWII which is an abbreviation for World War 2.

WWII which is an abbreviation for World War 2.