This is where my Golden Age (as Mister Silver Age wisely says) begins. Though that's not entirely true as my first comic was Justice League of America #103, but I read this one two or three years later.
I'm also going to split this up by issues at least for this three-parter.
This was Len Wein's first JLA issue as well as its 100th, so he had an anniverary to celebrate, to boot. How do you make this team-up special: you add another team! Strangely he doesn't think Teen Titans or Legion of Super-Heroes, he thinks about a little remembered Golden Age team. I'll speak about them later. First:
JUSTICE LEAGUE #100 (Au'72): The Unknown Soldier of Victory!
The conceit of this issue was that it was the JLA's 100th meeting. I will assume this meant regularly scheduled meetings, not emergancies. If the League met monthly then they've been around eight years, four months. If weekly, then it's less than two years, which seems unlikely.
The JLA: The entire active JLA roster is present here. This allows Aquaman to interact with the JSA for only the second time. There is the first (?) Green Arrow/Hawkman verbal joust. They hold this special event in their original mountain sanctuary, which is nowhere near Happy Harbor. Trust me on this! :-) There are guests though.
Metamorpho the Element Man: after saying "NO!" to JLA membership but becoming a "standby" member and had stood by for 60 issues, Rex finally shows up! Wein probably liked the character and felt the League needed a little muscle for this adventure, which it did!
Ralph Dibny, the World-Famous Elongated Man: Wein loved this guy! He only met the team once in #51. Met them, did not work with them---a long magical tale! But he would soon join in #105!
Zatanna the Magician: she worked twice with the JLA but several times with its various members. Besides why Wouldn't you want her at your party??
Diana Prince, Wonder Woman: this was a woman who felt humbled and would not have even came if Batman had not insisted even though she had more reason to be there than the other guests!
Then there were the cameos:
The Martian Manhunter: this FOUNDING member of the JLA was left out as most writers could not get a decent handle on him. Plus he was on Mars II though he would return for #115.
Snapper Carr: Unable to face his mentors after his actions in #77. He would also show up again in #114.
Adam Strange: Still on Rann. The most deserving "honorary" member had to stay home!
If the Elongated Man and Metamorpho who helped the JLA once were invited, why not Robin, Batgirl, Hawkgirl, Mera, the Creeper, the Earth-One Vigilante or Sargon the Sorcerer? Just asking why not? Wouldn't the wives want to go with their husbands?
The JSA: No new information is given but on hand were: Doctor Fate, Sandman, Hourman, Johnny Thunder, Doctor Mid-Nite, Starman, Wonder Woman, Wildcat and Red Tornado.
Fate brings the JLA to E-2 because of The Hand that Holds the Earth! Literally, a planetary size hand about to crush the Earth, created (somehow, despite no obvious technology nor the massive amount of energy needed to use it) by mysterious villain The Iron Hand.
Fate also with Zatanna and the Thunderbolt summon the cosmic Oracle who knows all of what happened and the past is his domain. He tells the two teams that the answer lies in a third team, one no one remembers, The Seven Soldiers of Victory (7SV)!
BTW, where were the E-2 Superman, Flash, Hawkman, etc? Strange that they would be absent?
The 7SV: their roster was: The Shining Knight, the Green Arrow and Speedy (of E-2), the Vigilante (of E-2), the Star Spangled Kid and *sigh* Stripesy and the Crimson Avenger!
No one remembers them because they were blasted into the past following their destroying of the Nebula Man. Oracle will send seven three-man teams into time to recover the missing Soldiers. He also tell them of the 7SV's first adventure against a crimelord, The Hand. Hmmm?
Now the 7SV were an unknown factor to readers in the 70s or were they? I know I read their reprinted adventure in JLA #111-112 before I read these issues, so I knew who they were!
In JLA #76 (D'69), a portrait of the 7SV was seen, complete with roll call.
In JLA #78-79 (F-Ma'70), the Earth-One Vigilante was revived. There were reprints in Action #403 (Au'71) and #405 (O'71). There were new stories in Adventure # 417 (Ma'72) and #422 (Au'72). He also teamed with Superman in World's Finest #214 (N'72).
The Shining Knight was re-presented in World's Finest #205 (S'71) and Adventure #417 (Ma'72).
Superboy #185 (My'72) had a reprinted Star Spangled Kid tale.
So if you read DC comics during that period, the heroes of the 7SV were familar to you.
Chapter 2: Doctor Fate, the Atom and the Elongated Man appear in Aztec Mexico where they battle a mesmerized Crimson Avenger, who thinks he's a Sun-god because of the powers given to him by a hunk of the Nebula Man that came with him. ICK! By destroying the nebluite, the Avenger is cured and they vanish!
Some Notes: Not to tweak a certain Morrison scholar, but The Nebula Man was originally described as an "awesome, giant Earth-man!" who conquered and killed until he was destroyed by the 7SV's "new weapon" at the cost of a Soldier's life!
Oracle was an intriguing character. Sadly he was not used again after this tale.
Next: Three Soldiers Trapped In Time or I Wanna Go with Superman!