Everything you need to know to start watching M*A*S*H

This article was sponsored by WGN America. Be sure to tune in to the All-Day All-Night M*A*S*H Marathon, Saturday, December 8th, starting at 9am/8am central.

The millennials out there know what I'm talking about. As kids, nothing made you keenly aware that your TV-watching session had run well past your bedtime quite like those distinctive opening chords and telltale yellow letters that meant a rerun of your parents' favorite show was coming on.

But now that we're all grown up and don't need a constant stream of slapstick comedy, cutesy characters, and teenage drama to sustain our attention, it's time to revisit and start binge watching one of the greatest television shows ever made — and I promise your dad didn't tell me to write this.

Before you dive in (you'll thank me later), here's what you need to know to start watching M*A*S*H.

Inside a real MASH operating room during the Korean War, from a real-world Korean War doctor, Dr. Robert L. Emanuele of Chicago.

(Photo by Dr. Robert L. Emanuele)

A MASH was a real thing

In the Korean War, a MASH unit was a frontline medical unit, a Mobile Army Surgical Hospital. Wounded troops would be treated by a medic or corpsman, then taken to an aid station if necessary. Once there, if they needed more care, they would be evacuated, sometimes by the newly-developed helicopter, to a MASH for surgery. These units were as close as ten miles to the front.

What later became a movie and a legendary TV show, M*A*S*H got its start as a book, written by Richard Hornberger under the pen name Richard Hooker. Hornberger was a real-life surgeon in a MASH unit and the book documented a few things the author says were based on real events — though he never says which ones.

While the setting of the series is important, it's all the characters that really drive the show. Here's who you'll meet:

Alan Alda as Hawkeye Pierce.

Capt. Benjamin Franklin "Hawkeye" Pierce

Hawkeye is a talented surgeon and pacifist from Maine who was drafted at the outset of the Korean War. He won't use a weapon but he'll let himself be sent to the front line if it means it'll save a life. Like almost everyone in the 4077th, he enjoys a drink after work, even going as far as constructing a still in his tent, nicknamed "the Swamp." His nickname comes from the book, The Last of the Mohicans.

Wayne Rogers plays Trapper John.

Capt. "Trapper" John McIntyre

Trapper is Hawkeye's best friend on the camp for the first three seasons of the show (actor Wayne Rogers left the series after season three) before being replaced by Capt. BJ Hunnicutt. Trapper, a former football player at Dartmouth, was drafted from a hospital in Boston and was sent home from Korea before the end of the first year. He shares a tent with Hawkeye and Maj. Frank Burns, and spends his spare time drinking and chasing nurses.

Loretta Swit as Maj. Houlihan.

Maj. Margaret "Hot Lips" Houlihan

Major Houlihan is the chief nurse at the 4077th, a career member of the Army Nurse Corps, and a military brat – her father was an artillery officer. She's a by-the-book kind of officer and the most capable nurse in the OR, but she's carrying on an illegal relationship with Maj. Frank Burns.

With Frank, she is constantly battling the practical jokes from Hawkeye and Trapper and doesn't respect the leadership style of the 4077th's commander, Lt. Col. Henry Blake, who she is constantly trying to undermine.

Larry Linville as Major Burns.

Maj. Frank Burns

In the U.S., Frank Burns is an Army reservist with his own successful practice who married into a wealthy family in Indiana. In Korea, Major Burns is carrying on an illicit affair with Major Houlihan and, with her, trying to undermine the authority of Lt. Col. Blake. Despite his higher rank, Burns isn't respected as a doctor, having flunked out of medical school twice. His actions in and out of the operating room reflect his ineptitude in medicine and in life.

McLean Stevenson as Lt. Col. Blake.

Lt. Col. Henry Blake

Henry Blake is an Army reservist and the commanding officer of the 4077th who was sent to Korea after asking a general if he took cream and sugar with a coffee enema. Blake is also a skilled surgeon but a chronic alcoholic. He's a friend to Hawkeye and Trapper and puts medical needs ahead of Army formalities. He knows he's not the best choice to be a commander of anything, but asserts his authority when needed.

Blake was sent home in the third season of the show and replaced by Col. Sherman Potter for the rest of the series. But the producers famously wrote a final scene into the third season finale that only Alan Alda knew about as they were filming the episode. It wasn't until they finished shooting the regular script that the actors were told, and they filmed the final scene where Radar announces that Henry Blake's plane was shot down over the Sea of Japan.

Cpl. Walter "Radar" O'Reilly 

Gary Burghoff was the only actor to play his character in both the 1970 M*A*S*H film and the CBS television show. He's the company's enlisted clerk, and one of the only two enlisted recurring characters, the other being Cpl. Max Klinger. His nickname comes from the fact that he acts on orders before they're given and can predict things before they happen.

Cpl. Maxwell Klinger

Corporal Klinger was only supposed to be an extra in one episode, but viewers loved Jamie Farr's character so much he was brought back in the regular cast for the rest of the show. Klinger was drafted from Toledo, Ohio, and is constantly looking for ways to get kicked out of the Army, most famously trying to be considered crazy and get a section eight discharge for wearing women's clothes.

Capt. B.J. Hunnicutt 

Captain Hunnicutt was a young doctor fresh out of residency when he was drafted and replaced Trapper John at the beginning of the show's fourth season. Where most of the other doctors are loose with their morals when it comes to women and war, Capt. Hunnicutt is true to his wife and the Hippocratic Oath.

He still enjoys having drinks with his colleagues, though.

Col. Sherman Potter

Colonel Sherman Potter is also a fourth season replacement, coming in for the dearly departed Lt. Col. Blake. Unlike Blake, Potter is a career U.S. Army surgeon who pays closer adherence to Army regulations – though hardly as strict as Maj. Houlihan and Maj. Burns would like. He fought in World War I as an enlisted cavalry troop at age 15 who was captured by the Germans. He later earned a commission after going to medical school in the years between World Wars. He was also in the Battle of the Bulge in World War II.

It's not known how old Col. Potter is during the Korean War.

Maj. Charles Emerson Winchester III 

Major Winchester is a classically-trained physician and surgeon from an aristocratic family who isn't accustomed to the "meatball surgery" performed at a MASH unit. He enters the show in season six as a replacement for Frank Burns who went crazy after Maj. Houlihan got married to someone else and was promoted out of the Korean War for it.

Winchester gets stuck at the 4077th after winning so much money betting against his commanding officer in Tokyo that his CO exiles him to the Korean War. He's a much smarter, more conniving foil to Hawkeye and BJ's antics.

Father Mulcahy 

Father Mulcahy is an Irish-Catholic chaplain at the 4077th and is surprisingly non-judgemental about the extramarital affairs of the unit's doctors and nurses. Even though most of the staff is not religious (and Klinger is an avowed atheist), everyone treats the Chaplain with respect – even more because he tends to win all the base betting contests and poker games.

Things like not saluting superior officers.

So, how do Army officers get away with all this stuff?

As you can imagine, talented surgeons were hard to find in the Army. Of course some existed, but in a war like the Korean War, the numbers of military surgeons working on the front lines were augmented by conscription – in other words, they were drafted. The doctors of a MASH unit were doctors first, then Army officers if time allowed.

Writers, actors, and producers of the TV show M*A*S*H actually spoke with and interviewed many MASH doctors at length to get ideas for the show, so at least some of the antics you see on the show were grounded in reality. Again, they never specify which ones.

Now that you've read this primer, the only thing left to do is dive into the show and experience it for yourself. And believe me, there's a reason why the show captured the attention of an entire generation of TV fans.

Be sure to tune in to the All-Day All-Night M*A*S*H Marathon, Saturday, December 8th, starting at 9am/8am central.