Greetings... ahalan wa sahalan...

In (ahem) "U.S. Military English," that expression equates to

[1] Draft Notification or Draft Notice

[2] Conscription Notification or Conscription Notice.

Such notification letters include details of where and when the recipient must report for processing and induction into compulsory (draft) military service (that period of full-time service used to be a two-year tour of military training and duty assignments in a unit before the US Army converted into an all-volunteer army).

Hope this helps.

Khair, in shaa' Allah.

Regards,

Stephen H. Franke
San Pedro, California