I agree a major problem especially with young soldiers away from there girlfriends the first time was Dear John letters.
In most cases it was AWOL rather than outright desertions.
Once you are gone 30-days and listed as a deserter, you can be arrested by any law enforcement agency for desertion and returned to military control Normally, most of these people were punished by Article 15, UCMJ, non-judicial punishment, stripped of rank, fined, and then put under some type of Administrative Chapter for getting rid of them and getting them out of the military.
It is usually some type of personal, financial, or failure to adapt problem, rather than what the leftist press wants you to believe that they ran off for anti-war crap. Now, some may have ran off simply because maybe they had been deployed over to Iraq once, twice, etc., and just were not going again. It was not because they were anti-war, but rather they were anti-having to go overseas and serve again, without girl friend or mama to baby sit their sorry asses.