A documentary exploring the joys and hardships of cadets as they work towards becoming officers in The Salvation Army will air on the BBC this week.

In order to gain the title of officer, members must give up their jobs, enrol in two years of training, live in assigned housing on campus and work full time for The Army for an annual pay of just £7,500.

The documentary follows several cadets as they make this journey, bringing to light stories of personal calling, transformation and a desire to practically live out Jesus' commands.

Officers-in-training must sign a declaration in which they promise "to care for the poor, feed the hungry, clothe the naked, love the unlovable, and befriend those who have no friends". It is a key moment in their training, as it signifies their commitment to uphold The Salvation Army's values and make the saving of lost souls their primary motivation.

"Sign if it's where your personal passion intersects with the world's compelling need," cadets are told in the one hour thirty special, perfectly summing up the heart of The Salvation Army's message.

Beyond the uniforms and army structure, we see cadets chatting with street cleaners they've come to know by name, befriending homeless people and spending time in brothels, bringing compassion and a listening ear to women in the sex industry.

Jesus' command to look after those in need is lived out and met by people of faith who are responding to and motivated by a God-given calling.

"I just want people to get Jesus, to have the opportunity to meet this Jesus that I love," says one cadet.

The documentary does not paint an altogether glossy or perfect picture of life as a Salvationist, however. As we are given an intimate look into the lives of those families and individuals who have made the life-changing decision to train at William Booth College, the sacrifices they make are uncovered. First year recruit Darren has left a successful career as a baker to pursue his calling, while young married couple Cathy and Luke Johnson moved to William Booth with their two small children a year ago to begin the course.

The deep issues that cadets struggle with are sensitively unearthed, namely the reconciliation between faith and doubt. Each person interviewed admits to experiencing periods of questioning and unbelief, but the conclusion is made that doubt is, in fact, an essential element of an authentic, real faith.

"Some people say doubt is the opposite of faith, it's not. Doubt is a part of faith. That's honest," says Captain Steve Dutfield, Course Tutor at William Booth.

Training Programme Director Major Malcolm Marton agrees: "People with doubts says to me that they are people who are open to exploring, understanding, to broadening their understanding."

The programme offers a fresh perspective on an organisation as known for its brass bands as for its Christian charity, and reveals the people behind the mission, who make big sacrifices to see the lost come to know and love God.

God's Cadets: Joining the Salvation Army will air on BBC Four on Tuesday 7 January at 9pm.