Warning: This article contains spoilers for Peaky Blinders season 6.

Peaky Blinders season 6 starts with the resolution to season 5's cliffhanger, as well as answers as to who prevented the assassination of Mosley, and why. The Peaky Blinders season 5 finale left both fans (and Tommy himself) wondering why his seemingly foolproof assassination plan went so wrong. It turned out, though, that its failure was even worse than initially thought. Here's how the IRA found out about the assassination attempt, and whether or not Mosely knows too.

Tommy's assassination plan for the leader of the British Union of Fascists, Sir Oswald Mosley (Sam Claflin, who returns as part of Peaky Blinders season 6's cast), ended in bloody disaster, with the deaths of his men Barney Thompson, and Aberama Gold. Mosley, meanwhile, seemed none-the-wiser and more powerful than ever. At the start of Peaky Blinders season 6, Tommy returns home from his own failed suicide attempt. He receives a telephone call, saying, “I imagine you’re curious as to who it was prevented the assassination,” as a van deposits the bodies of his people at the front door.

Related: Peaky Blinders' Season 6 Will Make The Original Tommy Casting Even Worse

The voice belongs to Captain Swing (Charlene McKenna), the Irish Republican Army (IRA) leader in Belfast. She tells him that it was they who thwarted Tommy's assassination plan and killed his men. However, she also says that the IRA has taken the opportunity to "restructure" the Peaky Blinders' organization, with Tommy seeing there are three bodies wrapped in white sheets, not two. Tragically, the third belongs to Polly Gray, Tommy Shelby's Aunt and matriarch of the Shelby family. Here's how the IRA knew about the Mosley assassination plan, why they saved him, and why they betrayed Tommy by killing Polly.

Billy Grade Informed The IRA About The Mosley Assassination

Peaky Blinders Billy Grade

In the last episode of Peaky Blinders season 5, Tommy's younger brother Finn Shelby naively talked about the assassination plan to Billy Grade, a supposed ally of the Peaky Blinders. Finn gives him a roll of money as a bribe for his silence, but once he's alone, Grade reaches over the money to the telephone and makes a call. Peaky Blinders season 6, episode 5, confirmed that Billy was the one who leaked Tommy Shelby’s assassination plan to the IRA. Billy meets his end at the hands of Duke, after Finn refuses, in the Peaky Blinders season 6 finale. But, only after Tommy uses him to lure the IRA into a trap.

Why The IRA Want Oswald Mosley Alive In Peaky Blinders Season 6

Oswald Mosley gives his fascist speech to the British public in Peaky Blinders

The IRA foiled Tommy's assassination attempt on Mosley as their interests were partially aligned. Captain Swing informs Tommy during their telephone call that the IRA needs to keep Mosley alive, and that's all Tommy needs to know. It's later revealed in Peaky Blinders season 6, that the IRA wanted to align with Mosley because they were searching for more power. Mosley has indispensable connections with America, and the IRA assumed that keeping Mosley in control (and alive) would help bolster their chances of acquiring more money and resources by working with the USA. Certain parts of history only support this.

In 1920, before his depiction in Peaky Blinders, Mosely was a Conservative member of Parliament and Secretary of the Peace with the Ireland Council. However, he split with Lloyd George’s coalition government after denouncing the treatment of the Irish by the UK government, particularly the violence of the Black & Tans. The Black & Tans were constables recruited in the Royal Irish Constabulary (RIC) as reinforcements during the Irish War of Independence. They had a reputation for brutality and reprisals against civilians after IRA attacks. Mosley believed the Black & Tans' savagery was disgracing Britain's name and thought that Ireland should be free to govern itself. Historians debate whether this position was just posturing to make a name for himself in parliament (which it did).

Related: Peaky Blinders Season 6 Proves The Show's Impossible Problem

Whatever the driving force of his political position and ambitions that led him to become Peaky Blinders ultra-fascist Mosley portrayal, there were some cross-sympathies between his extremist political views and that of the IRA, only supported by the Peaky Blinders season 6 revelation. His reputation as a crusader for Irish independence was later used by his party to attract Irish emigrants to his fascist cause. Additionally, both Mosley's followers and the IRA were nationalist extremists in their individual countries.

Why The IRA Killed Polly In Peaky Blinders

Peaky Blinders Season 6 Episode 1 Polly

Polly's murder at the hands of the IRA is a shocking way to start Peaky Blinders season 6, and Tommy breaking down upon discovering her body is heart-breaking. Such a brutal act, though, is a strategically clever move by Captain Swing. She talks about making changes to the structure of Tommy Shelby's organization and removing his “crutch,” that he's leaned on for his successes — which is Polly. The IRA put the responsibility for her death on Tommy, as they think he consistently fails to understand his own limitations. Over previous seasons of Peaky Blinders, it's been shown time and again that Polly is the one who can get through to, and influence, Tommy. Tommy is more vulnerable without her guidance and ability to keep his head cool. With his “crutch” removed, the IRA believes that he’ll be more reliant on them as a result.

Peaky Blinders season 5 saw Tommy Shelby as a member of Parliament himself, working various angles and infiltrating both communist and fascist parties in service of his own agendas. This destabilizing of the UK government is of the benefit of the IRA’s cause. Polly’s murder (and presumably also Ada Shelby’s partner Ben Younger in Peaky Blinders season 5), shows how far they’re willing to go to achieve their goals, and why Tommy has to do what he’s told (for now). Outside of Peaky Blinders' narrative, Polly's death on the show was inevitable given the sad passing of actress Helen McCrory, and episode 1 is dedicated to her memory. Polly's influence, though, is felt throughout Peaky Blinders season 6, as Polly's son Michael blames Tommy's ambition and strategies for her death, and swears revenge. The result of that grudge comes to a head in the series finale, when Tommy finally shoots Michael through the head after a failed attempt on his life.

Why The IRA Turn On Tommy Shelby, Despite Season 5

Peaky Blinders Season 6 Episode 1 IRA

Peaky Blinders season 5 planted the seeds for the IRA to work with Tommy Shelby, rather than turn on him. After they capture Michael in Belfast and claim that he's planning on betraying Tommy, the IRA asks whether Tommy wants them to kill him or set him free. Per Tommy's request, Michael walks free, but the IRA says that since Tommy's "conversion" to socialism, he's on the side of the angels, which is useful to the IRA's cause. The implication is that a mutually beneficial partnership is on the cards.

Related: Peaky Blinders: Every Character Who Could Return For The Movie

Though the nature of characters within the gangster show is inherently duplicitous, the IRA betraying Tommy Shelby in Peaky Blinders season 6 at first appears to be in direct contrast to what was set up in season 5. Polly's death, though, is a statement of the IRA's power and reach, with the intention of it being a lesson to Tommy not to overstep his bounds. Though his assassination plan for Mosely failed, without Polly's death, Tommy might have been convinced to try again. With adversaries now on all sides, he needs to be more cautious. Peaky Blinders season 6, episode 1, has Tommy explaining to Michael that Polly's death won't go unanswered. But when dealing with such a powerful enemy, he has to pick his moment. Tommy Shelby finally gets that moment when he feeds Billy false intel and lures the IRA into a shootout at Garrison's pub.

Why Didn’t Mosley Know About The Assassination Attempt?

Oswald Mosley delivers a speech announcing the formation of his facist party in Peaky Blinders

Mosely was seemingly unaware of the assassination attempt at Tommy's hands, though he did leave the party early because he feared that his life was in danger. While Peaky Blinders season 6 does tie up a lot of loose ends, this is one glaring plot hole that remains. Not much additional info is available on this front, with IRA frontwoman Captain Swing dead after a shootout in which Arthur avenges Polly's death at the Garrison Pub. The rest of Peaky Blinders season 6 focuses on Tommy's and Michael's burgeoning duel, which ends with a misplaced car bomb, and Tommy shooting Michael through the head. In addition, Tommy also finds out that his diagnosis of inoperable tuberculoma was a lie.

Since the doctor's setup was somewhat connected to Mosley and Diana, it is possible that Oswald found out about the assassination. The false diagnosis was designed to make Tommy more unhinged, but because Tommy quit drinking, that didn't exactly go according to plan. Whether Mosley knew about the assassination attempt is likely to remain unresolved because of Billy's death. Billy informed the IRA about the attempt on Mosley's life, and he could've had information on whether or not Mosley was made privy to this. The information would undoubtedly persuade the fascists to help the organization in their quest for power. The upcoming Peaky Blinders movie should provide a satisfying answer, though based on Dr. Holford targeting Tommy, it's probable that Mosley already knows.

Next: Peaky Blinders Season 6 Ending Explained (In Detail)

New episodes of Peaky Blinders season 6 air on Netflix in the US on Friday, June 10th.