The rigors of combat and the expectations of a soldier on the front lines may directly conflict with a person's religious or moral beliefs. If a person is firm in their convictions and they've proven they're serious about their beliefs, they may apply to be recognized as a conscientious objector.
Being opposed to war is not a Get Out of War Free card. Simply read the stories of Medal of Honor recipients Cpl. Desmond Doss, Cpl. Thomas W. Bennett, and Specialist Joseph G. LaPointe and you'll learn that being a conscientious objector doesn't even mean you'll be taken off the front lines.
Additionally, conscientious objection is too often confused with pacifism and cowardice — but this is far from the case. Watch Hacksaw Ridge (if you don't want to read the book it's based off, The Conscientious Objector) and you'll quickly see what we mean.
What the status actually does give a troop is a way to aid their country while remaining faithful to any beliefs that prevent a troop from personally engaging in combat.
To be labeled as a conscientious objector, a troop must prove to the military that their convictions are firmly held and such beliefs are religious in nature. The status is not given for any political, sociological, or philosophical views or a personal moral code.
Potential recruits in today's military cannot enlist with any conscientious objections. Such an issue is plainly addressed in a question presented to all recruits at MEPS. It asks,
"Do you have any religious or morale objections that would hold you back from participating during a time of war?"
In an all-volunteer military with many applicants who aren't conscientious objectors, answering this to the affirmative could bar them from enlistment.
It's also not entirely uncommon for troops who are already serving to become conscientious objectors, typically when faced with a combat deployment. Troops are then sent in front of a board to determine if their beliefs are genuine or not. If approved by the board, the troop is then classified as either a 1-0 Conscientious Objector, which honorably discharges them from service, or as a 1-A-0 Objector, which leads to a travel to non-combatant duties and prevents them from handling weapons.
The 1-A-0 status was the classification for the Medal of Honor recipients, like Cpl. Doss, who still saved the lives of countless men but were religiously opposed to fighting their enemy.
In the past, the U.S. military has needed men to fight and has employed conscription policies to fill out the ranks. If you were selected to serve, decided you didn't agree with the war (on whatever grounds), but were not recognized as a conscientious objector, you faced fines or jail time for refusing to enter service. No conflict saw more applications for conscientious objector status than the Vietnam War.
Unfortunately for the many who were opposed to the war, a political footing doesn't exempt you from service. While previous wars saw exemptions for Anabaptists, Quakers, Mennonites, Moravians, and various other churches, disagreeing with U.S. policy wasn't going to keep you from the fight.
Those who think conscientious objectors are just afraid to fight may be surprised to learn that many folk with religious objections will often opt to be 1-A-0 objectors and enter the service as a non-combatant, like a construction or medical work, as was seen with most Amish men drafted during WWII.
Conscientious objectors could also opt to do Civilian Public Service — where they'd stay stateside and perform duties as firemen, park rangers, and hospital workers.