What is history of planet reach?

Answer 1

Reach was discovered in the 21st century by UNSC forces were before the covenant attacked in the game halo reachDon't listen to these y and colonized in 25th century. ONI discovered a sacred Forerunner artifact that the covenant were afraid of decimating it, so that's why they sorta spared it, and also every spartan was made, from 150 eligible candidates, among John, Sam, Fred, members of omega and noble six, were in there after being scouted and abducted by Dr. Halsey and Captain Keys. 75 survived, they were created for using against the insurrection, pretty much rebels of the unsc. Then when the covenant came they were used, and eventually the covenant found out about the relic. When the Iroquois destroyer ship returned with a covenant spy drone attached, the covenant hit Reach, and the small unsc army and the MAC guns on reach was not enough to save reach... and the unsc abandoned reach, hence the term Fall of Reach

Spartans 2's were made about 30 years before these events

It had changed the war or something like that between the Humans and the Covenant? How?