Yes. Unlike the Combat Infantryman Badge, Expert Infantryman Badge, and Combat Action Badge - which are Group I awards - the Combat Medic and Expert Field Medic Badges are Group II awards. The CAB was intended for personnel who are not eligible for the Combat Infantryman Badge. Contrary to what was previously stated, not everyone who serves in an Infantry unit is eligible for a CIB. A Combat Medic in an Infantry unit does not get awarded a CIB, for example. If that unit has dedicated communications personnel assigned to the unit, they're not eligible for the CIB (however, someone with an 11B MOS who is serving as a radiotelephone operator is eligible for a CIB).
One interesting contrast with the CAB vs. the CIB and CMB is that the CAB is awarded - at least in theory - only to those who make direct contact with the enemy, whereas the only requirements for the CIB and CMB is that you spend 30 days in a zone for which the award is authorised, whether you make contact or not. Truth of the matter is, there are plenty of CAB recipients who have legitimately earned it - there's also a good number of fobbits who've received them because some mortars landed on the opposite side of the camp they were at.
By the way, the Combat Medic badge is no longer exclusive to line medics - from 2001 to 2004, the Army revamped it's MOS classification system. The MOS of 91B (Combat Medic) was removed, and was folded into the MOS of 68W (Healthcare Specialist) - which encompasses a much broader range than the old 91B MOS did. Thus, you have medics being awarded CMBs who've never so much as left the FOB.
They could be worn together, as the CIB and EIB are Class 1 badges, and the CMB is a Class 2 badge. However, to be able to do this, you'd have had to serve in combat in one MOS (infantry or medic), then reclass your MOS, and serve in combat in the other MOS.
Infantrymen could test for the EFMB, and medics could test for the EIB. I went through EIB testing and completed it. However, since I never held an infantry MOS, I couldn't wear the EIB, just the same as infantrymen who tested for EFMB but never actually held the MOS of 68W ("healthcare specialist"... combat medic was 91B prior to the reorganisation) and completed it still couldn't wear the EFMB.
Medics cannot receive CABs (Combat Action Badge). Instead, they receive the CMB (Combat Medical Badge) for treating wounded soldiers in a combat situation.
If he's under fire, yes. The Army has a special case: if a medic assigned to an infantry unit treats a patient under enemy action, he will receive the Combat Medical Badge rather than the Combat Action Badge. Medics in non-infantry units will receive the Combat Action Badge.
The combat action badge are worn with "Class A" Army green, blue or white uniform coats. You must wear that uniform when wearing the badge.
On the left breast, 1/4 an inch over the U.S. Army tape.
AR 670-1
The Combat Action Badge (CAB) is specific to the U.S. Army and is awarded to soldiers who have actively engaged or been engaged by enemy forces in combat. If you switch from the Army to the Air Force, you will not be authorized to wear the CAB unless you have previously earned it during your time in the Army. The Air Force has its own combat-related awards and badges, such as the Air Force Combat Action Medal (CAM).
Whatever badge/ribbon you are awarded, you rate to wear it, no matter what branch of service you are in.
So long as you have earned them, yes. The President's Hundred tab, Special Forces tab, Ranger tab, Combat Infantryman/Combat Medic/Combat Action badge, parachutist wings, Air Assault wings, scuba qualification badge, Pathfinder badge, etc. are individual awards which can be worn by a soldier who has earned them, regardless of if they change units or MOS.
JUST GOOGLE "US ARMY BADGE PLACEMENTS" AND THAT SHOULD SEND YOU TO SITE THAT WILL GIVE THE ANSWER AND MORE!
No. They would receive a Combat Action Ribbon. If ever they transferred to the Army, then they'd be eligible to wear the CIB or CAB in lieu of their Combat Action Ribbon.
Why would you want to? The CAR means more to a Marine, and hold the equiv of an Army CIB. Also, you can NOT transfer a CAR to a CIB.
The question makes it sound like a scenario where one decides to switch from the Regular (active) Army to the Army Reserve in the middle of their enlistment. This cannot be done - you can reenlist into a reserve component after your enlistment in the Regular Army is up, but you can't decide halfway through your enlistment that you want to switch your status to that of a reservist. On the matter of wearing an EIB, yes. You're entitled to wear any skill badges earned regardless of which component of the Army you're in. If you've earned the Expert Infantrymans Badge, Combat Infantrymans Badge, Expert Field Medic Badge, Combat Medic Badges, Combat Action Badge, jump wings, Air Assault wings, Pathfinder Badge, etc., then you're still entitled to wear them if you reenlist for a reserve component of the Army. Same thing with a Ranger tab.