It depends on your definition of "large". The biggest seen in WWII were army groups, made up of two more more field armies, with hundreds of thousands of troops. A field army has two or more corps in it, and might have 75,000 to 300,000 men. A corps has two or more divisions in it, and might have from 40,000 to 120,000, roughly. A division has three regiments (or brigades) in it, and might have 10-15,000. A US regiment in WWII had about 3300 men, and had three battalions in it. A battalion had three rifle companies, plus a heavy weapons company, a total of about 850 men. A company (in the US) had about 225 men when the war started; later, the table of organization changed and a company had 187 men when it was at full strength at the end. A company had four platoons, each with around 40-50 men. Each platoon had four squads, each with about 12 men.
A Battalion, a Regiment, a Brigade or a Division
They raised troops for the Union, but they also raised troops for the Confederacy.
'enemy'
The small northern state that was the first to issue a call for black troops was Massachusetts. This occurred during the US Civil War.
The were 4 States which left the Union after Lincoln call for troops: Virginia on April 17, Arkansas on May 6 Tennessee on May 7 and North Carolina on May 20, 1861.
John McCain's callsign was Playboy.
Soldiers on foot are commonly referred to as infantry.
George Washington called out the troops to put down the whiskey rebellion.
Callling in artillery was called "a fire mission." Calling in jets was called "an air strike." Ground troops engaging the enemy was called "CONTACT!" And it was yelled over the radio just as loud!
J. Steven Wilkins has written: 'Call of Duty' -- subject(s): Command of troops, Military leadership
A formation.
They raised troops for the Union, but they also raised troops for the Confederacy.
Federal troops are always a last resort when it comes to policing matters for a couple reasons: A. Troops' ultimate mission is to protect U.S. citizens from foreign threats. B. Government fears that troop activity in domestic territory may spark hostilities and resentment for the military. This hurts the image of, and respect for, military personel. C. That's what we have police for.
'enemy'
There was a period of military anarchy which historians call the Crisis of the Third Century. Emperors were military commanders who were proclaimed by their own troops. These were challenged by other military commanders who were hailed emperors by their own troops. There was a lot of infighting. Most emperors were murdered, sometimes even by their own troops who had elevated them as emperors because they did not want to fight civil wars. There was also hyperinflation, which crippled trade and the economy. This situation was brought to an end and the empire recovered. However, it did not return to its previous prosperity.
A military scientist
The Little Corporal.
They called American troops "Gringos"