For the first time in decades, Yale students will today attend courses on campus as part of the Reserve Officers’ Training Corps.

Twenty-one students are participating in the return of a program that left campus in 1972, amid protests against the Vietnam War. Yale’s restored Naval and Air Force units are smaller than those typical of ROTC programs — with 11 and 10 Yale students, respectively — and they lack a senior class to provide leadership. But ROTC officials say the units will grow over time, and they are adapting the program’s leadership structure to fit the makeup of their younger cohort.

“You can’t hold more than one leadership position, so there are going to be some incoming freshmen and sophomores who have never seen or done anything with the military who will have leadership positions,” said Andrew Hendricks ’14, an Air Force cadet. “But it will have us communicate better as a team and work harder if we want this to work out.”

In light of the U.S. military’s “don’t ask, don’t tell” policy barring gays and lesbians from serving openly, ROTC units remained absent from campus until the policy was repealed in December 2010. The University signed agreements with the Navy and Air Force over the next few months allowing both service branches to reinstate their ROTC programs on campus.

The newly formed naval unit is composed of 10 freshmen and one sophomore, while the Air Force unit has no Yale seniors and only four juniors. Col. Scott Manning, Yale’s Air Force ROTC commander, said he expects that older cadets will assume leadership positions, and that instructors will take extra steps to “mentor and groom this initial group.”

In an effort to develop a chain of command for the new naval unit, ROTC officials will select the unit’s platoon commander and sergeant from among the underclassmen today, based on their performances during a Aug. 11-18 orientation. Lt. Molly Crabbe said larger groups of midshipmen, which can reach hundreds of students, would rely on seniors to assume various leadership positions in the unit.

“Here we don’t have that, and we have to artificially give them that environment,” she said.

The Navy’s 11-student ROTC unit consists of only Elis, while the Air Force has created a consortium with nearby schools — including the University of New Haven, Quinnipiac, Southern Connecticut State and Western Connecticut State — which brings the unit’s total to 43 cadets.

Crabbe and Manning said recruiting for their initial class met expectations, adding that they believe the units will grow over time. Crabbe said she expects the Navy to recruit at least 11 midshipmen per year in the future, and Manning said he hopes to see the Air Force unit “explode” with 50 Yale cadets and 100 outside cadets.

“Just the intellectual capability that Yale brings to those who wear the uniform, and even the cross-towns who will take classes with professors like Paul Kennedy, you can not put a price tag on how that will influence the thinking and development of the U.S. Air Force as an institution,” Manning said.

Yale’s Navy and Air Force ROTC units were established in 1926 and 1946, respectively.