Start by going through the Basic Training for the character's nation. Then, pick a military career (at the bottom) of the page:
"You'd never know it to look at me now, but twelve years ago I was this runnynosed punk from Liverpool who thought he was the toughest cat in the jungle. I figured I was tough enough to conquer the Army in no time, then spend the rest of my enlistment strutting about in my uniform, impressing the birds.
"Then, at basic training, I met my drill instructor, Corporal Watson. He was smaller than me, but built like a rugby player, with a voice that would do a cannon proud.
"He taught me three things. One, that any notion of toughness I'd picked up fighting other punters in the gangs in Liverpool was rubbish. Two, that he was going to rebuild me as a soldier, whether I thought he could or not.
"And three - there was, despite all indications, a real soldier in me after all. I eventually became a corporal in the Grenadier Guards. If it weren't for Corporal Watson, I'd still be a punter in Liverpool, on the dole—you call it "Welfare" in America."
All characters entering the army receive basic training. This training varies from nation to nation, but it tends to follow guidelines established by one or another of the major powers.
US Army
American-style basic training lasts between eight and eleven weeks, depending on the nation concerned.
Skills: The character receives the following skills in basic training:
Armed Martial Arts: 0
Autogun: 0
Grenade Launcher: 0
Ground Vehicle (Wheeled): 1
Small Arms (Rifle): 2
Swimming: 1
Tac Missile: 0
Thrown Weapon: 1
Unarmed Martial Arts: 1
Special
Characters with Intelligence and Education > 13 may enter OCS. If so, they receive a level 1 Leadership skill, are commissioned as 2nd lieutenants, and conduct their first term normally.
Soviet-Bloc Armies (Cold War) and Communist-Bloc Armies (Modern Era)
Officially, Soviet basic training lasts four weeks, followed by a five month advanced training cycle that is repeated three times during a draftee's two-year term.
Skills: The character receives the following skills in basic training:
Armed Martial Arts: 0
Autogun: 0
Grenade Launcher: 0
Small Arms (Rifle): 2
Thrown Weapon: 1
Unarmed Martial Arts: 1
Special
Soviet bloc armies don't have OCS in the same way Western armies do. However, troops often go to "Higher Military Schools" upon completing their enlistments. Treat as Military Academy for characters who qualify.
Commonwealth Armies
Includes Great Britain, Canada, Australia, New Zealand, and South Africa (at least during the Cold War), as well as Israel. Commonwealth style basic training is more involved than most, lasting twenty two weeks in the British Army, with similar terms in other nations using this system.
Skills: The character receives the following skills in basic training:
Armed Martial Arts:2 (much bayonet training)
Autogun: 0
Grenade Launcher: 0
Ground Vehicle (Wheeled): 1
Small Arms (Rifle): 2
Swimming: 1
Thrown Weapon: 1
Unarmed Martial Arts: 1
Special
Characters with Intelligence and Education > 13 may enter OCS. If so, they receive a level 1 Leadership skill, are commissioned as 2nd lieutenants, and conduct their first term normally.
See also the section on the Commonwealth Regimental system—it's an important part of any Commonwealth character, especially career officers and NCOs.
Third World Armies
Including China during the Cold War (but not Modern) era. The length of time involved varies widely between nations. Some countries conduct Soviet or American style terms of formal instruction, while others merely give a recruit a rifle and tell him to obey or die. This chart sort of splits the difference.
Skills: The character receives the following skills in basic training:
Small Arms (Rifle) 1
Melee Combat 1
Thrown Weapon 1
Special
Characters with Intelligence and Education > 13 may enter OCS. If so, they receive a level 1 Leadership skill, are commissioned as 2nd lieutenants, and conduct their first term normally.
Characters may pick their Army career path from the list below.
Army aviation is generally but not always transport and attack helicopters, as distinct from the Air Force and Naval Aviation.