Alex Morgan is an agent with Intrepid.
Intrepid (sometimes displayed in all caps) is an acronym for the "Intelligence, Recovery, Protection and Infiltration Division". The division the name indicates is that of Interpol. While most of the world consider Interpol to be a law enforcement advisory agency, in this storyline, it has learned that policing the many and varying types of genocidal and xenocidal groups in the world today requires people willing to do far more than just advise.
In the first of the recorded adventures, it is stated that "Intrepid agents are hand picked from across the world. Part policeman, part soldier, part spy, they are the faceless, unassailable strangers among us - serving the world and operating beyond the influence of the most powerful nations." The agents for Intrepid are often referred to as 'Defender'.
One of these Defenders is Alex Morgan. As the series begins, he has been an agent with Intrepid for likely a short time after training because while he has had several missions under his belt already, the mission he is sent on is his first solo action.
It is important to remember, though, that while he might be fairly new to Intrepid, he is by no means new to extreme danger while going up against an assortment of very unpleasant opponents.
Before being enticed to join up by British Major General "Nobby" Davenport, Morgan had been for many years a member in the 3PARA, the British Paratroop Regiment, considered by most to be one of the most elite of the UK Special Forces. For some time he was attached to the 75th Ranger Regiment in Afghanistan where he learned to work closely with the Americans and learned just how good they were, and they learned how very capable he was.
In the pages of the adventures, we do not learn much about Morgan's life before his Intrepid days except that the action he saw in the military was frequent and bloody. We can surmise from the fact that he held the rank of Major before leaving that he had to have been in the service for a good number of years so we can estimate his age to be early 30s.