The Minutemen are a major faction in Fallout 4 and the first to be introduced in the main quest. However, the player's interactions and quests with the faction are not exactly that explorative when it comes to the Minutemen's actual history and complicated political past. There is far more to them than just helping people and forming relationships with settlements.
By the time players meet the faction in Fallout 4, much of the leadership and members have died. Preston Garvey is all that is left of the leadership before the protagonist is able to sign on to the group. This is in the year 2287, a hundred years after the Minutemen truly rose to prominence in the Commonwealth.
The Minutemen 100 Years Before Fallout 4
The Minutemen first became a big deal in 2180, when they protected Diamond City against a large assault of super mutants. After gaining positive attention and trust with the people of the Commonwealth in the coming 50 years, they made an alliance with regional settlements and attempted to create a provisional government in the 2230s.
The Institute was going to be involved in this government, as they had not totally shut themselves off from the surface yet. However, they decided to back out. This led to the CPG Massacre Incident, with a synth killing all settlement representatives. This ended all future attempts to organize a united Commonwealth and began igniting the fear of the Institute.
It is unknown how long the Minutemen used Fort Independence as their base in Boston. They renamed it The Castle, and used it as their base and armory until 2240, when a mirelurk queen destroyed parts of the landmark. This killed their general at the time, General McGann, as he became trapped during the attack and died alone with only wine to consume.
Another general from their history was Joe Becker, who came many years after McGann and the fall of The Castle. How he died is unknown, but it was on or before the year 2282. He has been described as a good leader and his death was before the collapse and in-fighting that would eventually befall the faction. His successor was never chosen, as no one could agree on who should replace him. The loss of the leader with no replacement made some Minutemen leave the faction altogether, while others began infighting. People like James Wire even went from being a Minuteman to a Raider. However, the Minutemen never stopped helping people and responding to any requests for aid.
The Quincy Incident
When the Quincy Incident happened, a group of Minutemen (which included Preston) were under the leadership of Ezra Hollis. Hollis was in charge of one of the last active Minutemen squads in the Commonwealth, and they came to Quincy to respond to pushing back against Gunners attacking the town. The mayor of Quincy, Jackson, let the Minutemen use his own house as barracks for defending against the Gunners.
The Gunners were quite strong, so Hollis reached out to the few other Minutemen left for help, but they did not respond due to political infighting. The tides fell into the favor of the Gunners when a 10-year Minuteman veteran, Clint, defected and joined the Gunners. The Gunners rewarded him with a lieutenant rank, and he led the second attack on the town.
Clint personally captured Hollis alive and killed him in front of the Gunners to prove his loyalty. Hollis was loyal to the Minutemen in the end, never giving up as Quincy fell. Preston took whatever survivors he could under his protection and escaped Quincy. Clint sent Gunners after them, and the survivors slowly fell in number as they were killed by feral ghouls before making it to the Museum of Freedom. Word spread about the Minutemen's failure to protect Quincy and this made much of the Commonwealth lose their faith in the organization.
Fallout 4 is available on PC, PS4, and Xbox One.