Last Friday, Conan O'Brien bid The Tonight Show adieu. Jay Leno will reclaim the "King of Late Night" title in March. But to understand the present, one must know the past: here's how we got to where we are now.

On his show last week, David Letterman commented that he'd known Leno for some 35 years. And, it would appear, the two were friends at some point. But was Leno's ascension to the Tonight Show throne in 1992 really what started the bad blood between the two men? We begin our exploration of the relationship between them—and those caught in the crossfire of their feud—more than 25 years ago.

Note: Events (and videos of them) are grouped and labeled by the year in which they occurred, unless otherwise noted.

1984: As you'll see in this interview of Leno by Letterman on Late Night, it seems Leno may have had it out for him from the get-go, as he filibustered away before telling Letterman, "I've been telling the network [it doesn't need you] for 18 months."

(To see Letterman's interview with Leno in its full, awkward glory, click here.)

1992: On May 22nd, after 30 years as host of The Tonight Show, Johnny Carson stepped down amid a flurry of controversy, which focused on two main issues:

  • First, there was the issue of Carson's retirement, as some believed that Leno—who had served as guest host for Carson for years—forced NBC's hand and encouraged the network to facilitate Carson's hasty retreat from the airwaves.
  • The other issue, of course, was over who would succeed Carson. The problem here was that both Leno and Letterman had convincing arguments to take over The Tonight Show: Leno had served as Carson's guest host for years and had established a relationship with the brass at NBC, but Letterman—as host of Late Night, which followed The Tonight Show, also wanted the job. And while Carson never spoke publicly about the battle to succeed him, several published reports suggest that he would have chosen Letterman.

Given the aforementioned, it should come as no surprise that Carson chose to have Letterman on his show one week before his retirement, effectively snubbing Leno. In these clips from May 15, Letterman jokes with Carson about the fact that he was not chosen to succeed him. (It should also be noted that Carson made rare appearances on The Late Show with David Letterman on CBS following his retirement, but never visited The Tonight Show with Jay Leno.)

Later that year, in an interview with Barbara Walters, Letterman said he was "not sure" why he hadn't been chosen to take over The Tonight Show.

1993: After being passed over for Leno, Letterman was courted by CBS to host his own show at 11:35 PM. In his final broadcast on NBC before moving to CBS, Letterman poked fun at the situation (O'Brien replaced Letterman as host of Late Night on NBC the same year).

And on August 30—during his first show on CBS as host of The Late Show—Letterman further poked fun at his strained relationship with NBC, including reports that his former network would exercise its rights to "intellectual property" from his previous show, thereby forcing him to retire certain elements of it as he moved networks.

At this point, even though bad blood between Letterman and Leno was widely reported, it seemed neither host would touch the topic publicly. In this interview from the same year, Leno addressed the issue of whether or not he was nervous about competing against Letterman, and was sure to reassert that it was all business.

1995: For the first two years that Leno competed directly against Letterman, he came in second place in the ratings. It wasn't until this July 10, 1995 interview with Hugh Grant—shortly after Grant had been arrested for soliciting a prostitute—that Leno came out on top, a lead he then held almost constantly for nearly 15 years.

Recent revelations about the early-to-mid 1990s would suggest that Leno was more than just a shrewd businessman. Here's one example, courtesy Rosie O'Donnell, who claims she was asked by NBC to do Friday nights for Leno—something that would have made her career—before the offer was rescinded on Leno's "selfish" insistence. In this recent clip from her radio show (which was rebroadcast on The Howard Stern Show), O'Donnell recounted the 1995 incident.

2004: In 2004, NBC had two wildly successful late night broadcasts in The Tonight Show with Jay Leno and Late Night with Conan O'Brien. The network faced a predicament, though, in that it had one host who would seemingly never retire on his own accord (Leno) and one host who had grown weary of the 12:35 AM time slot (O'Brien). NBC's solution was to avoid O'Brien leaving the network and competing against Leno at 11:35 PM by promising him The Tonight Show in five years and—in what some would celebrate as karma, delivered more than a decade later—forcing Leno into a 2009 retirement.

On the surface, everything seemed fine. Leno used his September 27 broadcast to announce that O'Brien would replace him in five years, reiterating to the audience that he wanted to avoid any of the animosity that resulted from his replacement of Carson 12 years earlier.

Shortly thereafter, O'Brien announced on Late Night that he'd be taking over The Tonight Show when Leno retired, and personally thanked Leno for going gracefully.

2006: If O'Brien thought Leno would go gently into that good night, he was one of the only ones. In this Late Night clip from December 14, Howard Stern warns O'Brien that Leno may not give up his show that easily.

2008: As O'Brien's debut on The Tonight Show grew closer, NBC was faced again with the problem it had attempted to solve in 2004: what to do about Leno? A month before the apparent solution—NBC's announcement that Leno would host an hour-long primetime show, weekdays at 10:00 PM—Artie Lange stopped by Late Night and O'Brien was given yet another warning about the future.

2009: On February 11, Norm MacDonald made his last appearance on Late Night and said what everyone else was probably thinking: Leno had outfoxed his competition yet again by demanding the 10:00 PM time slot.

Even with all of the warnings, though, the handover of the Tonight Show reins to O'Brien went forward, and Leno even had his successor on as his final guest on May 29, saying, "You were the only choice, you were the perfect choice."

2010: It's clear now, though, that NBC—and Leno—felt differently. After only seven months as host of The Tonight Show, O'Brien was forced off the air last Friday, and Leno is set to reclaim the late night crown on March 1.

(Special thanks to Gawker Media video intern Alison Flood for her assistance with the research for this project!)

For our complete coverage of everything related to the Late Night Wars, click here.