[Stealhead]

I would call ISIS fighting tactics as light infantry I would call the FSA and Kurds style of fighting the same. They are not an insurgency in the areas they control. I would agree that ISIS seeks to have an insurgency style of terror in areas that is dose not control.

In the US OG means original gangster or a gang member that has survived some time as a member of his gang. For example Snoop Dog said in a song "OG of the LBC". Meaning Original Gangster of the Long Beach Crips. You can also ask Ice T. I learned much about street gangs in the military because the military is a better option than jail for some folks.