BZZZZZZZZT!!! I'm sorry, that's an incorrect answer. But thanks for playing! We're going to send you home with some lovely parting gifts, including the home version of our game, "Everything You Know is Wrong." you may now turn around and tell our studio audience, "I am not smarter than a 6th grader!"
The idea of Trinity is biblical -- probably equates to similar, pagan ideas of the time the texts were written, but that was in the first century -- not the third, and certainly before the church became the official religion of the Roman government. The idea of the Trinity wasn't "forced" on anyone. It was solidified by the ecumenical council that met at Nicea in 325. IOW, it was a consensus decision.