The IDF is taking the unprecedented step of enlisting young men who are learning in hesder yeshivas, but are not officially part of the hesder program. The men in question would previously have had a deferral under the Tal law, which exempted full-time Torah students from military service.
They were presumably planning to enlist in the military after studying in yeshiva for one or two years, as is customary in the hesder program. In the five-year hesder program, men learn Torah for three and a half years and serve in the IDF for eighteen months rather than the standard three years.
Sources in the hesder system said agreements are being formed that would allow the young men to remain in yeshiva if they officially join hesder.