The Raid

Indonesian special tactics officer Rama prays, practices silat and bids goodbye to his father and wife, who is pregnant with his child. He cryptically promises his father he will "bring him home." Rama joins a heavily armed 20-man elite police squad, including Officers Bowo and Dagu, Sergeant Jaka, and Lieutenant Wahyu, for a raid on a high-rise apartment block in Jakarta's slums. The team intends to capture crime lord Tama Riyadi, who, along with his two lieutenants Andi and Mad Dog, owns the block and lets criminals around the city rent rooms under his protection. Arriving undetected, the team sweeps the first floors and subdues various criminal tenants; they also temporarily detain an innocent, law-abiding tenant delivering medicine to his sick wife in apartment #726. Continuing undetected to the sixth floor, the team is spotted by a young lookout, who passes on the message to another adolescent lookout just before he is shot dead by Wahyu; but the latter youth raises the alarm.
Tama calls down reinforcements and the SWAT team are brutally attacked. Thugs snipe two officers guarding the perimeter, eliminate two more in the SWAT van, and ambush several officers patrolling the first five floors. Cutting the lights, Tama announces over the PA system that the police are trapped on the sixth-floor stairwell, and he will grant free permanent residence to those who kill the intruders. In the darkness, the remaining team members are ambushed by shooters from above and behind, and the team is almost completely wiped out. Prior to the gunfight, Wahyu confesses to Jaka he has staged the mission so he can eliminate Tama, who is in league with many corrupt police officers, including himself. The mission is not officially sanctioned by the police command; nobody at HQ knows their location and thus there is no hope for reinforcements.
The remaining officers retreat into an empty apartment only to be cornered by more armed henchmen. To create an escape route, Rama uses an axe to cut a hole in the floor so that the team can descend to the lower level. Dropping to the room below, the SWAT team once again struggles to fend off Tama's horde of thugs and Officer Bowo is critically injured in the process. In a last-ditch effort to defend his team, Rama uses a stove propane tank to construct an improvised explosive device that successfully eliminates the invading henchmen, giving the officers a small window of time. With more of Tama's reinforcements approaching, the team splits into two groups: Jaka, Wahyu, and Dagu retreat to the fifth floor, while Rama and a critically injured Bowo ascend to the seventh in search of the law-abiding tenant they encountered earlier.
After fighting through a handful of goons on their way to apartment 726, Rama and Bowo plead with the tenant for help, and despite his sick wife's protest, he reluctantly hides the officers in his apartment. Four machete-wielding thugs arrive and ransack the man's apartment, but fail to find Rama and Bowo. After tending to Bowo's wounds, Rama leaves him with the couple so that he can focus on searching for Jaka's group; however, he crosses paths again with the machete gang. Rama manages to defeat the group, including their leader, whom he uses to smash through a window and cushion a three story plummet onto a fire escape below. He then continues his search, only to be confronted by Andi, who has just murdered two of Tama's thugs in the elevator. Rama and Andi are revealed to be estranged brothers, and Rama signed up for the mission to search for him, at the urging of their father. Rama refuses to leave the building without his comrades, and Andi refuses to abandon his auspicious criminal life. Rama reluctantly accepts Andi's decision and parts with him in order to search for his remaining team members.
Meanwhile, Mad Dog and a squad of his thugs discover where Jaka and his group are hiding. A brief scuffle occurs which ends up splitting the SWAT team even furtherâthe thugs pursue Wahyu and Dagu while Jaka is left at Mad Dog's gunpoint. Instead of shooting him, Mad Dog challenges Jaka to a hand-to-hand fight which he ultimately wins before proceeding to snap Jaka's neck, killing him. Mad Dog subsequently meets up with Andi to report back to Tama in the surveillance room. Tama, having learned of Andi's treachery, incapacitates Andi and hands him over to Mad Dog for torture and execution.
Rama regroups with Wahyu and Dagu, who go on to fight through a narcotics lab, and they head for Tama on the 15th floor. Along the way, Rama discovers a room where Mad Dog is torturing Andi, causing him to separate from Wahyu and Dagu. Mad Dog allows Rama to free Andi and fights both brothers simultaneously. Mad Dog initially has the upper hand, but the brothers prove to be a match for him when working together. After an intense and grueling fight, Rama finally kills Mad Dog with Andi's help.
Meanwhile, Wahyu and Dagu confront Tama after managing to kill off his remaining henchman. Upon arresting Tama, however, Wahyu ends up betraying Dagu by shooting him dead before taking Tama hostage; intending to use him as a shield to escape. When the duo encounter Rama and Andi on the verge of leaving the building, Tama taunts Wahyu by revealing that he had been waiting for the team before the raid began and that Wahyu was set up by his corrupt higher-ups; also indicating that he will be killed regardless of escaping. In despair, Wahyu kills Tama and attempts suicide, only to find that he has no bullets left.
Andi uses his influence over the tenants to allow Rama to leave with Bowo and a detained Wahyu. The tenant who protected Bowo watches from a window and grins with delight. Andi also hands over numerous blackmail recordings Tama made of corrupt officers taking bribes, hoping that Rama can use them to his benefit. Rama asks Andi to come home, but Andi refuses, due to his acclimation to his criminal lifestyle. Before Rama leaves, Andi asserts he can protect Rama in his role as a gang lord, but that Rama could not do the same for him. Andi turns around and walks back to the apartment block with a grin that breaks into a wide smile, while Rama, along with Wahyu and an injured Bowo, exits to an uncertain future.

Question: What did Rama join?
Answer: A heavily armed 20 man police squad.