Corporals need the opportunity to be corporals before they become sergeants. That's what Sergeant Major of the Marine Corps Troy Black told Marines recently when introducing new enlisted promotion and retention policies. Starting in January, corporals won't be able to pick up sergeant until they've been in the Marine Corps for four years. That's twice as long as the current requirement. And sergeants won't make staff noncommissioned officer status until they've served at least five years -- a year longer than currently required. Sergeants will also need 36 months' time-in-grade before they can make staff sergeant. That's up nine months from the 27 required now. Read more on Military.com.