Charles Schulz had a specific tradition every Veterans Day--he'd draw a strip about Snoopy, usually decked out in a non-WWI Flying Ace uniform, going over to cartoonist Bill Mauldin's house for some root beers. 
Mauldin was a cartooning sensation during WWII, but by the time I was growing up, I'd never even heard of him. I think Schulz knew that--look at this one, where Linus basically acts as an interpreter for the audience.
This particular strip, for example, was incomprehensible to me as a kid. I'd never seen Mauldin's work, so the Willie and Joe punchline didn't land.
The Veterans Day strips were as constant as the ones where Lucy pulls the football from Charlie Brown, but aren't as beloved mainly because Schulz was interested more in honoring Mauldin than landing a particularly good gag.
Especially toward the end of Schulz's life, the strips dispense with humor altogether. Schulz didn't particularly enjoy his stint in the service during WWII, but the farther he got from it, the more he seemed to commemorate it.
I don't know what sort of relationship had with Mauldin, but if I had to guess by the strip, I'd say that it was warm. Schulz clearly thought of him as a master.
This one is from 1987, an acknowledgment of their aging.
This is one of my favorites, if only because Schulz is nakedly praising Mauldin through the character of Linus. It's a sweet tone for an often melancholy strip.
But if I had to give a favorite, it's this one. It's a Veterans Day strip more in keeping with the Peanuts' tone, and grapples with how most of the audience most likely was receiving these Mauldin strips.
This strip isn't from Veterans Day, but touches on similar themes, perhaps more to an extreme, since Sally is younger than the rest of the characters.
A late-period entry, after Schulz had scrapped the four-panel structure. Again, the jokes are dispensed with--or the very idea of drinking root beer with Mauldin is the joke.
There is some variation. Here's some earnest praise for Ernie Pyle, the sort of strip that Schulz wouldn't have done for anyone else.
And if you think Schulz couldn't have combined two of the most frequently recurring strips in Peanuts, think again.
The Snoopy on the battlefield motif--as opposed to on his doghouse Sopwith Camel--became more frequent later on. Here's a particularly poignant Veterans Day strip from the 90s.
Anyway, there are numerous other examples, mostly with the same setup. Drinking root beers with Bill Mauldin on Veterans Day was one of the longest and most recurring themes in Peanuts. A shame that it isn't as well known as the Great Pumpkin and other such ideas.
