The recent U.S. military moves related to the Israel-Gaza conflict have raised questions about the American mission.

Here's why they're about deterrence:

2,200 US Marines aboard 3 ships

Where are the Marines? The 2,200 Marines from the 26th Marine Expeditionary Unit are aboard three U.S. Navy ships as part of their regular deployment to the Middle East.

Those three ships sailed away from the U.S. together as an Amphibious Ready Group but then they split up as needed. That’s why two of the ships, the USS Bataan and USS Carter Hall, were in the Arabian Sea Tuesday after having left the Persian Gulf earlier this week.

The third ship, the USS Mesa Verde, is in the Mediterranean only because it had to undergo repairs in Spain.

It left port this week with about 650 Marines and sailors aboard and is moving eastward in the Mediterranean. But it has not been given orders to head to the eastern Mediterranean as was done with the USS Gerald. R. Ford aircraft carrier, but it will be available if that order is given.

Will the Marines on these ships head to Israel? There has been no decision to send these Marines or ships close to Israel, but on Tuesday the Pentagon confirmed that they are being moved into positions where they could be close by if an order is given on short notice. A U.S. official said that no orders have been given but that the USS Bataan and USS Carter Hall will head towards the Red Sea and the USS Mesa Verde will remain in the Mediterranean

Why are they in the news? Because they are a U.S. military asset that would be available on short notice to assist with the potential emergency evacuation of U.S. personnel or others. They’re not going to be involved in any fighting. And they have no formal orders to be involved right now, they’re just moving to get closer in case they’re needed.

What can these Marines and ships do? The USS Bataan looks like an aircraft carrier and carries a mix of helicopters, vertical take-off Ospreys, and Harrier jets. Those aircraft could be used to rescue people on short notice. The USS Mesa Verde and USS Carter Hall carry water landing craft and ground vehicles.

2,000 US troops told to be ready to head to Middle East on 24 hours notice

Are they headed to Israel? No, if they are needed they will be sent to other areas of the Middle East.

Who are these troops? Defense Secretary Lloyd Austin has ordered about 2,000 troops in the U.S. and elsewhere to be ready to head to the Middle East on 24 hours’ notice instead of the normal 96 hours. This is what the Pentagon calls Prepare to Deploy Orders, which has the acronym PTDO.

So, 2,000 military personnel from the various military services have been told to be on PTDO on 24 hours’ notice. They are not combat troops but units that have specific job skills that might be needed in the Middle East. On Tuesday, the Pentagon confirmed that the units include those that specialize in air defense, security, logistics, medical support, intelligence, surveillance, reconnaissance, and transportation and other capabilities.

Why have we been told these troops might be going to the Middle East? Earlier Tuesday, the Pentagon released a formal statement acknowledging that these 2,000 troops were on PTDO orders. Why? They want to make it known that the U.S. is ready to provide additional forces to the Middle East if needed as a deterrent.

Making the potential deployment is part of that deterrent value directed towards Iran and Hezbollah.

The 2 US carriers

Why are there two carriers? It’s all about deterring Iran and Hezbollah from getting involved. Having one carrier was a strong deterrent. Having two carriers is a very strong deterrent.

Having two carriers available in the same region is extremely rare and was only possible right now because the USS Ford was headed home after a six-month deployment to the Mediterranean and the USS Eisenhower was just heading out for a Middle East deployment via the Mediterranean. As of Tuesday, the USS Ford’s deployment has been extended indefinitely.

How long the two carriers remain operating together is up in the air. The Eisenhower may take another 7-10 days to get to the eastern Mediterranean.

What’s a carrier strike group? When a carrier heads out on a six-month deployment it leaves port with a mix of cruisers and destroyers known as a carrier strike group. They leave port together but don’t always end up being together for the whole deployment. The purpose of these ships is to protect the aircraft carrier from attack and to have them available to head elsewhere as needed.

What can the two carrier strike groups do as a deterrent? Each carrier carries dozens of aircraft, mostly fighter aircraft.

The Ford is the largest aircraft carrier in the U.S. Navy and can carry up to 75 planes while the Eisenhower can carry up to 60 aircraft.

The presence of up to 120 U.S. fighter aircraft in the eastern Mediterranean is a deterrent to Hezbollah and Iran that they can help with Israel’s security if needed.

Where things stand right now they are not going to go into combat in Israel, but deterrence is all about strategic ambiguity so the message to Hamas and Israel is don’t get involved.

But if they are needed, they will be able to use their fighter aircraft for what they are intended for -- and right now they are using the surveillance aircraft aboard to gather intelligence about what’s around them.

Additional US aircraft to Middle East

What’s their deterrence value? Announced last week, the Pentagon has deployed additional F-35s, F-16s and A-10 fighter aircraft to the Middle East to show that the U.S. can show Iran and Hezbollah that it can quickly flow in more aircraft as needed -- as a deterrent.