O p e r a t i o n M e t e o r
Before Quatre headed towards the earth, have you ever wondered why he would accept the mission of Operation Meteor? Well, it goes a long way back. All the way when he was young.
At the age of 13, he was on board a plane. The Maganac held Quatre as a prisoner so they'd make Mr. Winner give up the workers he was using and let them go back to the earth. Mr. Winner agreed to let the Maganac Corp use his resources to get the workers back to earth. During this time, Quatre told his father how he was just useless and how he was used to take care of his father's resources. Rashid stepped up to Quatre and struck him in the face. (slap?) Quatre was furious but when he heard that the Maganac Corp were also test tube babies, he felt an extreme admiration for them. Even though they knew they were test tube babies, they live life knowing this and can still be happy.
Sometime later, Instructor H told him that the Maganac Corp are people who live proudly no matter how they were born. Quatre soon understood that a person's birth doesn't make him who they are. It's what they do with their life. When a traitor attacks Rashid, Quatre goes in and blocks for him. They both take the hit but Rashid's wound is not as serious. Despite that fact, Quatre goes out to fight with the Maganac. The other Maganac members question why he fights with them. He replied saying he hasn't proven himself worthy of pride and being a Maganac. Quatre says he'll get stronger and go to earth then. He'll join the Maganac there someday on earth. A little while later, Instructor H has almost finished Gundam Sandrock. Unfortunately, Mr. Winner doesn't support violence. Instead, Quatre decides to help the Instructor and go to earth against his father's wishes.
Instructor H questioned why he decided to help him. Quatre said that he wanted to be someone... with pride. So he goes to the earth using Instructor H's gundam. He believes that if no one fights back, the war will never end. Quatre rather he suffered the fighting and let others enjoy the peace. It is indeed a sacrifice that is great. Sort of like he's taking-other-people's-place-to-go-to-war kind of concept. Even though his father refused, he went with Operation Meteor. Quatre wanted to see the Maganac Corp too. He believes it's the right thing. And it will bring peace if he goes.
Knowing well what the plan will do to earth's citizens, he went on ahead anyway. The Alliance has just gone too far to try and suppress the colonies.