Many spoilers ahead for Episode 17 of Arrow Season 6, called "Brothers in Arms." If you haven't caught the episode yet, feel free to check out some of our non-spoilery articles until you get the chance to watch.
Season 6 has not been a good time for Team Arrow. Although the good guys of Arrow started out more or less unified in the sixth season, the team split when the newbie half discovered that the Original Team Arrow trio had been spying on them. With the trust broken between them, Dinah, Curtis, and Rene decided to leave Team Arrow and form Team Arrow-less. Okay, maybe that's not what they call it, but it's not like they have an archer in their ranks. Oliver, Diggle, and Felicity remained on Team Arrow, and their bond seemed unbreakable... until "Brothers In Arms" revealed a rift between Oliver and Diggle bigger than anybody could have predicted, and the episode ended with Digg leaving Team Arrow.
The atmosphere in the Arrow bunker was tense from almost the very beginning due to the fact that Oliver wasn't giving up the hood and returning the mantle of the Green Arrow to Diggle, who was honored and touched to be trusted with the responsibility in the first half of Season 6. Thanks to a chat with Thea before her departure, Oliver had decided that he was the best version of himself when he was the Green Arrow. As bad at communicating as ever, Oliver neglected to fill Diggle in on this development, and Digg was waiting for Oliver to return to his focus on his position as mayor and father. Oliver did eventually break the news and apologize for stringing his best bro along, and Diggle accepted the apology and Oliver back as leader and the Green Arrow.
That might have been the end of the conflict if Diggle hadn't continued with the self-reflection. After spending most of the episode considering the status quo on Team Arrow and having a heart-to-heart with his wife, Digg decided that Oliver wasn't a good leader to Team Arrow anymore. According to Diggle, Oliver may be the best version of himself as Green Arrow, mayor, father, and husband, but he's not the best leader for the team. Fortunately, because Diggle and Oliver are adults and such close friends that they consider each other brothers, they resolved this issue after a calm, frank, level-headed conversation.
Just kidding! After trading insults about all the people they've gotten killed, Oliver finally made a comment about Diggle killing Andy, and Diggle just went ahead and punched him in the face. Unfortunately, Oliver decided to fight back and give as good as he got. So, the gents of Team Arrow pummeled each other and destroyed a bunch of Felicity's tech before Felicity stormed in to stop them. They managed to mend fences enough to pull off one last mission to blow up a warehouse full of Vertigo. That wasn't enough for the two to mend fences entirely, however, and the episode ended with Diggle deciding that he no longer belonged on a team being led by Oliver. Team Arrow is now a twosome, and Oliver is the only fighting member left.
That said, Diggle isn't ready to give up on helping Star City, but he didn't even consider going to Team Arrow-less. Instead, he's joining Lyla at A.R.G.U.S., where he probably will be able to do a lot of good. He's a skilled fighter and tactician, and he could be an asset to the good guys at A.R.G.U.S. He could also help keep them on the straight and narrow, which has been a problem for them. I wouldn't be surprised if his access to A.R.G.U.S. comes in very handy before the end of the season.
A big question now is what Oliver is going to do now that Diggle is gone. Going out without backup is dangerous nowadays, and Team Arrow-less doesn't seem inclined to join him again. For her part, Felicity is a great resource from the Arrow bunker, but she won't be hitting the streets with him. The trailer for the next episode points toward Oliver not handling the new situation well:
It looks like Stephen Amell will be back in his original Hood suit for the next episode, which may mean a dream sequence and/or hallucination. Who knows? Maybe this will be the way that long-dead character turns up again. We'll have to wait and see. New episodes of Arrow air on Thursdays at 9 p.m. ET on The CW. If you need more info on all things superhero, check out our rundown of superhero TV dates. If you need some non-superhero options, take a look at our midseason TV premiere schedule and our summer TV guide. Arrow scored a renewal for another season, but not all shows have been so lucky. Swing by our rundown of network TV cancellations and renewals to find out the fates of many series.