In US military slang, an Iron Eagle is a military officer who has attained the rank of Colonel (OF-5) but will not be promoted to the rank of General (OF-6 to OF-9).

The term refers to the rank insignia a colonel wears, which resembles an eagle.

Reasons for Becoming an Iron Eagle

There are several reasons an officer may become an Iron Eagle:

• Administratively, certain occupational specialties are not structured to permit promotion to General without changing to a different career path.
• Other officers, for political or disciplinary reasons, shall never be promoted to General.

Career

Such officers sometimes retire, but others remain in the military for the full thirty years, until the service limitations (see Up or Out) of their current rank force their retirement.

Up or Out

Up or out, also known as a tenure or partnership system, is the requirement for members of a hierarchical organisation to achieve a certain rank within a certain period of time. If they fail to do so, they must leave the organisation.

In the US military, the 1980 Defense Officer Personnel Management Act mandates that officers passed over twice for promotion are required to be discharged from the military.

However, it has been criticised as “arbitrary and bad management” that forces out “many fit, experienced officers… because there were only so many slots into which they could be promoted.” Paul V. Kane, a Marine veteran of Iraq War and a former fellow at Harvard’s Kennedy School of Government, has argued that the “archaic ‘up or out’ military promotion system should be scrapped.”

Manning within the British Army plays a similar role.