Returning home: Roman Soldiers to Present Day
Many ancient cultures had their warriors perform purification rites before reintegrating into society. Water and actual washing is a recurring motif in many culture’s ceremonies. Moses’ army instructed warriors to ritualistically wash themselves and their virgin captives before returning to camp; Assyrian royal inscriptions detail the washing of weapons, a detailed description of Celtic warriors’ return in the Tain that involves them placing themselves in successive baths of water. 
Romans had both auxilia and legionary veteranus. Only about 3,000-3,600 men were annually discharged from auxilia service, and it was estimated about 36,000-50,000 auxilia veterans were alive as a demographic at any given time.  There were three possible auxilia discharge groups, which were with honor, without honor, and medical. The three categories held different privileges. Honorably discharged veteranus enjoyed special societal privileges, and received bronze diplomas upon their departures which guaranteed them rights to vote and marry. This was not able to be passed on hereditarily as it was with legionnaires. The higher class of soldier also enjoyed improved rights and wealth.
Soldiers varied in how often or much they stressed their military service, and in how much wealth they retained, with legionaries tending to be more prosperous than their auxilia counterparts. The missicus, who were soldiers discharged without honor before the end of their term of service, were considered marked men and had much more difficulty with reintegration.  Those who deserted had to take extra precautions to avoid the authorities. Turning to banditry was not uncommon for these men. Veterans attempted to integrate themselves into the local culture the best that they could rather than standing out as a group, returning to the cities they grew up in or served near and purchased land, but as a group are not considered to have been forces of cultural change in the manner other groups of veterans are thought to be.  There is evidence veterans sought one another out as neighbors, finding comfort in their shared service. Cities founded within newly conquered territory were called colonia, and were established for the purpose of Romanization. Thousands of retired legionnaires were granted land within such cities, and during the first century of the Roman empire the entire colony was composed of veterans who conducted the Romanization efforts. 
Penances for Medieval knights
Christian medieval knights, even those returning from church-sanctioned war, were expected to perform penance for their sinful actions during war before being reaccepted into society.  This reintegration process could take a long time. Some of the penances included a year of penance for each man killed, forty days for every man struck, and three Lents of penance for archers who did not know the number of those they killed. This led to increased feelings of guilt for many returned warriors.
Navajo culture had different kinds of ceremonies for returning soldiers.
When a soldier returned from war, his family could decide to sponsor a ceremony for him by contacting a spiritual leader, or medicine man, who then talks to the soldier about his wartime experiences and selects the most appropriate ceremony. The Enemy Way ceremony, sometimes called the Squaw Dance, is a Navajo ceremony used for soldiers who were in combat, captured, or wounded. These ceremonies veterans return to a state of “hozho” balance, or beauty, within the universe. Comanche veterans would partake of spiritually blessed peyote within a tipi and pray and sing. Many Native American tribes, especially those of the plains region, utilized a sweat lodge purification ceremony.
Veterans of the American Civil War...
Veterans of the American Civil War faced a great deal of difficulty and were treated with suspicion in the job market, especially those who had lost a limb in the war. There were not many resources to assist them with reintegration at first, but the Federal Pension Program was created in 1862 to provide monetary assistance to the growing number of those who could not work.  Union soldiers were covered on a federal level, while Confederate veterans’ states had to produce the money themselves. 
World War I veterans were underserved and misunderstood by their government, with posters telling them to “behave” designed by the Army for reintegration efforts acting as a fantastic illustration of how little their traumatizing experience was understood.  The War Risk Insurance Act of 1917 provided pensions for AEF soldiers, and the Vocational Rehabilitation Act of 1918 sought to provide disabled soldiers with vocational training.  The execution of the later program was botched, eventually leading to the Bonus March in 1932.  The American Legion also provided a pillar of advocacy for veterans, lobbying for jobs for vets and a payment to make up for lost income during the war.
The condition and symptoms we now associate with PTSD
The condition and symptoms we now associate with PTSD was referred to as “cardiac muscular exhaustion” during the Civil War, “shell shock” during WWI, and “combat exhaustion” throughout WWII and Korea. The advent of Vietnam brought about the term “post-Vietnam Syndrome” in the medical community, its creation aiming to give veterans a label to the mental and physical problems they experienced to clutch onto as they reintegrated into civilian life. It also helped mental health professionals assist these soldiers.