James Gordon was a Gotham City police officer, who later became Lieutenant and Commissioner.
Batman Begins
As a young police officer, James Gordon was freshly transferred from the Chicago Police Department to help the GCPD secure their city from an economic depression. After the depression came to an end with the making of a monorail system designed by billionaire Thomas Wayne, Gordon was on duty the night Thomas and his wife Martha were mugged and killed outside an opera by a criminal named Joe Chill, and responded to the situation. He did his best to comfort their orphaned son Bruce after the incident, and Bruce later recognizes him as one of the few honest police officers in the city and would always remember his kindness as it gave Bruce the strength he needed after his parents' death.
20 years later, after being promoted as a detective-sergeant on the force, Gordon was working late in his office when a man wearing body armor and a ski-mask visited him to ask about the mob boss Carmine Falcone's criminal operation and the police inability to stop him. When the man presses a stapler (which Gordon assumed was a gun) to the back of the detective's head, he told Gordon that together they could clean up the city. Gordon was unconvinced, simply believing the man to be "just some nut". Several nights later, people are starting to worry about Falcone's activities, but hope began rising in them, and Gordon, when he arrives on the scene of Falcone's capture at one of his drug shipment locations. Falcone's body, strapped to a spotlight, forms a symbol of a bat in the sky, enticing Gordon to realize that the man he met several nights earlier was serious about his intentions to bring down Falcone and his crime empire, and looked up with the other cops to see the man for the first time: a bat-masked figure with a cape flapping behind him, who was dubbed "Batman" by the press.
As news breaks of this new vigilante, Police Commissioner Gillian Loeb is infuriated that someone in his city has taken the law into their own hands and is being glorified for it. While Gordon stands up for Batman by stating that he finally took down Falcone, Loeb refuses to allow a vigilante handle their jobs and orders for a massive law force to track him down. Gordon finally meets Batman face to face outside his home one night while he is taking out the garbage. Batman informs Gordon of an ongoing conspiracy in Gotham that concerns Falcone and notes to Gordon that his corrupt partner Arnold Flass was assisting the drug smuggling, hoping to speak with him about the other drugs that the police weren't able to obtain.
Batman then trailed the drug smuggling to Jonathan Crane at Arkham Asylum, and Gordon went in to help him. Gordon escaped with Rachel Dawes, and delivered her to Batman. It would later be revealed that Crane was being used by Ra's al Ghul who is planning on dispersing the fear gas with a microwave emitter stolen from Wayne Enterprises and watch Gotham tear itself apart through fear. Ra's' men then orchestrate a massive breakout at Arkham, forcing Gordon to raise the bridges once all the riot police are on the island with him and attempts to apprehend the convicts. Rachel eventually meets with Gordon on the island and gives him the antidote for the fear toxin, given to her by Batman after saving her. Gordon then gets a patrol man to escort her to safety, but Ra's then begins to vaporize the water supply in the narrows, incapacitating everyone with fear. Gordon uses the antidote on himself and handcuffs Flass to a water valve after he attempts to murder two civilians while under the influence of the fear gas. Gordon eventually proves pivotal in Batman's defeat of Ra's al Ghul by driving The Tumbler to destroy a sectin of monorail and stop the microwave emitter from reaching the water board. However, Batman's actions inspired the criminals of Gotham to become more theatrical.
The Dark Knight
Nine months have passed since the Scarecrow's and Ra's al Ghul's reign of fear, and Gordon is now the leader of GCPD's Major Crimes Unit, a police sector created as Gordon's personal unit of his most trusted allies to work with Batman and newly elected DA Harvey Dent to bring down the new leader of Carmine Falcone's crime family, Sal Maroni, and the rest of the mob. By using marked bills, Gordon is able to track most of the mob's laundered money to five major Gotham Banks and persuades Dent to approve search warrants for them to search and seize the money. However, the mob is wise to this, due to Maroni's inside agents in Gordon's unit and Dent's office, and has the money transported to a secure location with the help of a foreign mobster named Mr. Lau. Because of this, when he found the vault empty save for marked bills, Gordon ended up kicking the stack in anger for what happened. While Lau leaves for his industries in Hong Kong, Dent and Gordon turn to Batman to get him back so that they may use Lau as a testimony to imprison the mob and cut off all their funds. Batman does so through an elaborate scheme and literally delivers Lau to Gordon outside his unit's headquarters.
While Lau refuses to hand over the money, he promises to testify against all his clients in exchange for immunity, protection, and a charted flight back to Hong Kong. Using this offer to testify, Gordon and Dent tied up the mob in a reco case and arrested many of them. All is going well until the Joker, a humorist psychopath who was hired by the mob to take out Batman, soon emerges onto the streets in a chaotic and violent fashion with the gruseome murder of a civilian. The Clown Prince of Crime then begins putting out hits on mob trial Judge Janet Surrillo, Loeb and Dent, giving Batman an ultimatum in the process; if Batman didn't reveal himself underneath his mask and turn himself in, then all three of his hits will die along with countless others each and every passing day. Gordon faked his own death at the attempted assassination of Mayor Anthony Garcia, then disguised himself as a van driver to drive Harvey Dent to safety. When the Joker attacked his convoy, Gordon caught him and arrested him. He was then promoted to Police Commissioner after the death of Loeb.
However, the Joker had kidnapped Dent and Rachel Dawes. Gordon tried to save Rachel but she was killed, so Gordon went to the hospital to console Dent. Gordon then had to protect Coleman Reese as the Joker put out a hit on him, but he was saved by Bruce Wayne. The Joker then held some doctors hostage, and Gordon had to deal with the situation. Batman went in alone, as Gordon received a call from Dent telling him that his family had been taken hostage. Gordon rushed to the warehouse to see Dent threatening his children, flipping a coin to decide whether they lived. Batman saved his son in the nick of time, killing Dent. Batman then persuaded Gordon to portray Batman as the villain and not tell anyone that Dent had gone insane. Gordon called it in as Batman drove away.
The Dark Knight Rises
Eight years have passed since the Joker's reign of chaos, and Gotham is thriving for the first time in decades largely thanks to the Dent Act - legislation inspired by Harvey Dent's "uncompromising stand" against organized crime, and his "sacrifice." With the newly installed Dent Act, any criminal connected to the Mob, regardless of their wealth or power, is imprisoned, denied parole, and denied the right to file an insanity plea, effectively wiping out organized crime in Gotham.