It is possible to be commissioned as a colonel or a General of a foreign army, by express designation of the Field Marshall of the foreign military. If you are given a commission you will receive a badge designating your rank and privileges - and this badge must be retained at all times. Examining the badge will inform you how much longer the commission will last. Below is a list of privileges and commands associated with a commission:
Syntax: INTRO <commissioning city>.
To differentiate your home city from the city of your commission (and who knows but you may hold numerous commissions) you should specify the name of the commissioning city here along with INTRO, where normally you would type INTRO CITY. So if Parrius has commissioned you, INTRO PARRIUS is used to interact with enlistables from that city.
Syntax: BECKON <commissioning city>.
Beckoning is a facility for bringing enlistables to your location, once you have distributed the appropriate enlistment passes. See HELP BECKONING for detailed info. To differentiate beckoning to your home city from beckoning to a commissioned city, you specify the foreign city in your BECKON e..g. BECKON MERCINAE to bring in the Mercinaen enlistables where typically you might use BECKON CITY to gather up home-city men.
Syntax: OBTAIN PERMISSION
The badge of commission allows you access to the barracks of the city responsible for your commission. You should OBTAIN PERMISSION in the normal way, while standing on the homesoil of the commissioning city and then make a beeline for the barracks, wherein you should find access permitted as if you were a local.
All of your military/dispatch goal interactions with legions of the commissioned army will be "as if" you hold the badged rank (i..e. colonel or General) providing the legion has been assigned to the 'Military' hierarchy or one of the open hierarchies. Your commission will not give you authority over 'Independent' or 'Personal' legions and the 'Authority' hierarchy will respond only to the General commisioned rank.
See also HELP COMMISSION for a broad overview of giving out commissions.