BRUNSWICK, Georgia — As they say, “Once a marine, always a marine.”

Will Cook served a stint in the Marine Corps and is going back, but the next time it will be to fulfill a calling to serve God and not only an oath to serve his country.

Cook is a transitional Catholic deacon serving a transitional internship at St. Francis Catholic Church in Brunswick. The ongoing pastoral service is the final year of a seven-year process that will culminate with his ordination as a priest on June 4 at the St. John the Baptist Basilica in Savannah.

The first six years were at the Notre Dame Catholic Seminary in New Orleans, and he’ll return there in October for another semester, Cook said.

From his squared away haircut to his spit-shined black shoes, Cook looks like a Marine in a cassock turned out for inspection.

His duties at St. Francis include assisting in the sacraments, and he has the authority to perform marriage ceremonies and assists at funerals.

Now 35, he started the process of becoming a priest in 2015, but he says the call came far earlier.

“Growing up, I always had a strong admiration for the priesthood,’’ but there were some things he did in between that helped the Tulsa, Oklahoma, native prepare including a degree in construction administration from Oklahoma State University.

Of his four years in the Marines, Cook says, “That kind of forces you to grow up.”

He was an air support control officer in Okinawa where he worked with the artillery as, he puts it, a step behind the infantry.” He was assigned to the Marine Corps Logistics Base in Albany, when he first came to Georgia.

If the Marines influenced him, so did a year of mission work with the Salesian priests in Nice in southern France, a Catholic religious order known for their charity work for children and the poor.

During that mission trip, he experienced contemplative, communal living with no personal possessions and working directly with the public.

The priesthood is not in line with how Cook said he imagined his future.

“I enjoyed my time in the Marine Corps,’’ he said, “but I wanted to work in the construction industry and have a family.”

It was while working construction renovating historic homes in Savannah in 2014 and 2015 that he felt called to the priesthood, leaving behind the possibility of marriage and a family.

“The mission trip taught me that you can be happy as a celibate male,’’ Cook said.

Priests are fathers to a lot of people, and parishioners look toward them for spiritual and fatherly guidance, he said.

“I think it’s OK to offer up that sort of sacrifice for the Kingdom of Heaven … It’s all a gift,’’ Cook said.

With his ordination next June, Cook will establish a sort of permanent spiritual home in a place he has come to love.

“I love Georgia. Oklahoma is great,’’ he said of his native state, “but I love Georgia and the low country. Savannah will always be my home diocese.”

That covers a lot of territory because the diocese encompasses the lower two-thirds of the state, but initially a lot of men and women in uniform will call him “Father.”

“I’ll be on loan three years as an active duty chaplain with the Navy and Marines,’’ he said.

Of his life to this point, Cook says, “It’s been a good 35 years.”

Counting his mission work, by the time he is ordained a priest he will have spent four years in the service of his country and eight serving God. It’s all been active duty.