Recruited by the Army in 2009 through the Military Accessions Vital to the National Interest (MAVNI) programme for his language skills in Punjabi and Hindi, Lamba completed basic training with his turban and unshorn hair at Fort Jackson outside Columbia and became a US citizen.
"I am thrilled to serve with my fellow soldiers and serve the United States of America," Lamba said.
"I humbly believe I was able to excel in all aspects of my training. Most importantly, I was overwhelmed by the support and camaraderie I felt with my fellow soldiers and base leadership. I thank them all and look forward to my service," he added.
Present US Army policy still excludes Sikhs who maintain their turban and beard. Sikhs in the US military may maintain their religiously-mandated turban and unshorn hair only if they receive an individual exemption to do so.
Lamba was initially told that his Sikh articles of faith would likely be accommodated.
But, in March 2010, his formal request for a religious accommodation was denied. Lamba appealed the decision, and his appeal was accepted in September 2010.
Contrary to the concerns of some, Lamba was able to meet all the requirements of a soldier during basic training.
He wore a helmet over a small turban during field exercises. During gas mask exercises, he successfully created a seal. He also enjoyed deep bonds with fellow soldiers and his superiors.
Present Army policy still excludes Sikhs who maintain their turban and beard. Sikhs in the US military may maintain their religiously-mandated turban and unshorn hair only if they receive an individual exemption to do so.
In 1981, the Army banned "conspicuous" religious articles of faith, including turbans and unshorn hair, for its service members.The ban was enacted despite a long history of Sikhs serving in the US military with their religious identity intact.
Nevertheless, the past year has seen welcome progress in the campaign to restore Sikh service in the US military.
In March, Captain Tejdeep Singh Rattan, a dentist, became the first Sikh commissioned officer to complete basic training in more than two decades.
In September, Captain Kamaljeet Singh Kalsi, a physician, became the second Sikh commissioned officer to complete basic training.
The addition of Lamba to the group of Sikh military graduates is a critical step forward in proving that Sikhs can successfully serve in the US military.
"To be an American is to be able to serve his or her country in the defence of the justice and equality we all enjoy as citizens. We appreciate the US Army's willingness to consider the overwhelmingly positive experiences of Captains Rattan and Kalsi - as well as the success of dozens of Sikhs who have served in the US. Armed Forces over the past century - in giving Mr Lamba the opportunity to serve the United States," said Amandeep Singh Sidhu lead counsel for McDermott Will & Emery LLP.
"We hope that his success in enlisted basic training continues to dispel misconceptions about the ability of a Sikh solider to conform to the Army's standards for neat and conservative uniformity, safety, military readiness, and unit cohesion," he said.
"We are grateful to the US Army and its forward thinking here. We are hopeful that the success Mr Lamba enjoyed during basic training will impress upon the US military the necessity of ending its general policy of Sikh exclusion," Amardeep Singh, Program Director Sikh Coalition said.
"Over the past year Sikh service in the US Army has been successfully tried and tested. We know it works. All Sikhs should now be welcome in the military. We look forward to working with military leadership to make that happen. Our military and the United States of America will be stronger for it."
Sikh soldiers served in the US Army as far back as World War I. Thousands of Sikh soldiers helped liberate France in WWII. Today, Sikhs serve in the militaries of England, Canada, India and Austria, among others, often alongside American soldiers in Iraq and Afghanistan.