die Army
U.S. Army
Specifically refers to the land forces of the United States of America (U.S. Army).
Er diente vier Jahre in der U.S. Army und war in Deutschland stationiert.
He served in the U.S. Army for four years and was stationed in Germany.

Army
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U.S. Army
Specifically refers to the land forces of the United States of America (U.S. Army).
Er diente vier Jahre in der U.S. Army und war in Deutschland stationiert.
He served in the U.S. Army for four years and was stationed in Germany.

'Army' is a word from English. In German, it is used with the feminine article 'die' and is usually pronounced as in English.
Die Army hat ein neues Rekrutierungsprogramm gestartet.
The Army has launched a new recruitment program.
In German usage, 'die Army' almost exclusively means the land forces of the USA (U.S. Army).
Viele amerikanische Soldaten der Army sind in Europa stationiert.
Many American Army soldiers are stationed in Europe.
Common expressions are 'zur Army gehen' (to join the Army), 'in der Army dienen' (to serve in the Army), or simply 'bei der Army sein' (to be in the Army).
Nach der Schule wollte er unbedingt zur Army gehen.
After school, he really wanted to join the Army.
army
'die Armee' and 'die Army' can both refer to military land forces. 'die Armee' is the normal German word and can refer to the military of different countries. 'die Army' is an English loanword and, in this context, refers especially to the U.S. Army, meaning the land forces of the United States. Learners may confuse the words because they look and sound similar. In German texts, people usually say 'Armee'. 'Army' only fits when the American Army or an English name is really meant.

Mein Onkel war mehrere Jahre bei der U.S. Army.
My uncle was in the U.S. Army for several years.
Viele junge Menschen leisten in diesem Land Dienst in der Armee.
Many young people in this country serve in the army.