(RNS) Even though men and women from every faith have been members of our armed forces since the Revolutionary War, the struggle for Catholic and Jewish chaplains to gain equality within the American military has been long and difficult.

It's not a new fight.

In 1775, the Continental Congress restricted military clergy to Protestant ministers. Rabbis and Catholic priests were banned from serving as chaplains until the Civil War. And even then it was not easy.

It required the personal leadership of President Abraham Lincoln to enact legislation that was adopted 150 years ago, on July 17, 1862: "No person shall be a chaplain in the United States Army that is not a regularly ordained minister of some religious denomination," the new law said.

The only requirement was presenting "testimonials of his present good standing as such minister" from a religious denomination that had at least "five accredited ministers."

The key word was "some," and there was no specific definition of what constituted an acceptable or recognized "religious denomination."

Catholic and Jewish soldiers were at last guaranteed their spiritual leaders would accompany them into battle. Indeed, Rabbi Ferdinand Leopold Sarner of Congregation Brith Kodesh in Rochester, N.Y., was wounded at Gettysburg in July 1863. And at least two rabbis also served as chaplains in the Confederate army.

In the years that followed, it became commonplace for pastors, priests and rabbis to work together in the military. The most dramatic example of such cooperation took place on February 3, 1943 in the icy North Atlantic when a German submarine torpedoed the U.S.S. Dorchester, a small jam-packed American troop ship carrying 902 men, headed for Greenland. 

The four chaplains on board -- Protestant ministers Clark Poling and George Fox, Catholic priest John Washington, and Rabbi Alexander Goode -- had become close friends at the Army Chaplaincy School. As the ship began to sink, the clergy colleagues helped move men onto lifeboats.

When it became clear there were not enough life jackets for all aboard, the four chaplains gave their own life jackets to others. The four men, holding hands in solidarity and reciting prayers, went down with the ship. They were among the 672 who died that night. 

As a result of their heroism, the so-called "four chaplains" were posthumously awarded medals for bravery, and a foundation was established in their memory to strengthen positive interreligious relations. A monument in Philadelphia commemorates the chaplains' act of courage.

In 1945, after the bloody battle to capture Iwo Jima, Navy chaplain Rabbi Roland Gittelsohn spoke at the dedication of a cemetery on that tiny Pacific island. His address endures as one of the great sermons in American history.

"Here there are no quotas of how many of each group are admitted. Theirs is the highest and purest democracy," Gittelsohn said. "Any man among us, the living, who lifts his hand in hate against another or thinks himself superior to those who happen to be a minority makes this an empty mockery."

Yet, it was not until 1972 that a non-Protestant, the Rev. John J. O'Connor, was appointed senior chaplain at the U.S. Naval Academy in Annapolis. O'Connor later became Chief of all Navy Chaplains.

The world later came to know him as Cardinal John O'Connor, the archbishop of New York. Next month, in a ceremony at the Vatican, Pope Benedict XVI will elevate another former Army chaplain, former Baltimore Archbishop Edwin O'Brien, to the College of Cardinals.

I served as a U.S. Air Force chaplain in Japan and Korea. Living day in and day out with my fellow chaplains provided me an important introduction to Christian-Jewish relations. At the time, my seminary classmate, Rabbi Philip Schechter, was an Air Force chaplain stationed in New Mexico.

Today his daughter, Sarah, is also a rabbi and wears the Air Force blue uniform as a chaplain. She has already completed seven years of active duty, including several deployments to Iraq.

Since 1862 all American clergy representing "some religious denomination" have been able to serve their country and their faith communities as military chaplains, both in times of war and times of peace. Thank you, President Lincoln.

(Rabbi Rudin, the American Jewish Committee's senior interreligious adviser, is the author of the upcoming "Cushing, Spellman, O'Connor: The Surprising Story of How Three American Cardinals Transformed Catholic-Jewish Relations.")