Witnessed this first hand in 1993, going through USAF electronics training at Keesler AFB, MS.
There were 5 foreign military students, Saudis if I recall correctly, in our class of about 30. They wore their nation’s uniforms, but on the collar, they wore small metal US insignia representing their equivalent US rank. Though they were all under age 30, they had the equivalent US military rank of SMSGT (That’s 7 stripes).
They were all idiots. We estimated their education level to be about 8th grade.
Half way though the 9-month program one of them just disappeared. The remaining 4 never gave us a direct answer as to where he went, but it was obvious he literally disappeared.