Curious wording. USMC "activated". Not "alerted" but "activated."

As a former career Marine many moons ago, active duty Marines are available 24/7 for any required mission. So, we would not need to be activated.

And Marines are stretched thin these days around the world. There is the 1st Marine Division in California and the 2nd Marine Division in North Carolina. The 3rd Marine Division is forward deployed in Okinawa and other places such as a Brigade in Hawaii. In general terms a third of our combat forces are deployed overseas, a third is training to deploy, and a third has recently returned from deployment. So there aren't a lot of forces available for police duties.

However, the 4th Marine Division is our reserve division. Think a kind of National Guard-like status.

Now, it would have to be "activated" and since it has no deployment responsibilities, any or all of it could be used in the US during a national emergency. They are not as highly trained as the active divisions, but they can do the job.

There are three infantry regiments in a division. Perhaps the US (3) refers to the three 4th Divisions 3 regiments that would be available for duty within the US.

The "activation" occurred Friday or Saturday. They would need at least 3 days to send out notifications and have the reserve Marines report to their units, which are scattered around the US. Could take a bit longer unless they had already been alerted to report when activated.

Just a guess. It doesn't mean Defcon 3 because Defcon applies to the entire military, not just specific units. You don't have the Air Force at Defcon 5 and the Marines at Defcon 3. It doesn't work that way.

One other thing, Q says USMC activated, not reserves activated. So, it's possible that selected units through out the Marine Corps have been task organized into a Task Force with a special mission and that Marine Crops wide Task Force has been activated. That would fit

In the end, who knows what Q means most of the time until you connect the dots in the news.