What’s the purpose of the Reserves?

We (the Army Reserves) are an inexpensive way to maintain highly capable forces available, if needed. You'll find that many support functions like; engineers, truck drivers, doctors, etc are far more capable on the reserve side, due to the high compatibility with their full time civilian jobs.

The National Guard is very specific, as they actually work for their individual state Governors. Many legal differences (Posse Commitatus) in how they are able to respond to disasters and civil unrest. The National Guard has its roots in colonial militias, whereas the Army Reserves is primarily designed to support the Active Duty with additional capabilities.

To augment the total Army force. Reserve and Guard Soldiers make up the majority of the Army's total strength... by a lot.

Well think of it this way. You have the Active Duty component. Strong, fit men and women ready to go at a moment's notice. Now what would you do if the Active Duty component wasn't enough? Then you start pulling from the Reserves. The Reserves for a lack of better words is our back burner just in case bodies.

If we had the draft, we'd be pulling from a mixed bag. Some fit, some fat. Some healthy, some sickly. Then we'd have to spend our time training them just to get them up to speed.

Instead we have the Reserves components. Men and women who are already dedicated to fighting on behalf of their country. They are already trained and receive continuous training a couple times a year to keep them ready.

I think it's funny that a Guardsman is asking about the point of the Army Reserves. The Reserves is like the National Guard, but we are federally owned as opposed to be state owned like the Guard. Like many have mentioned already, we augment the Active Duty. This really comes to play during long periods of operations. If you tried manning Iraq and Afghanistan with just the Active Duty, the Active Duty would break. The National Guard and Army Reserves lessen the burden on the Active Duty so that they are not constantly deployed.

One major difference between the National Guard and Army Reserve is that the Army Reserve is only composed of support MOS's. We do not have any combat arms except for Aviation. Aviation was switched from the Transportation Corps to a combat arms MOS in the early 2000s. The National Guard does have combat arms. Some states even have their own Green Beret units.

We all play an important part in maintaining operations around the world.

As most have said, it is cheap.

I think we also need to recognize the experience that goes with it. Sure I am a Reserve Warrant, but in my day role, I own an investment firm. Many others in my unit are cops, detectives, Federal Agents, Business Owners, Lawyers, etc. We even had a Congressman.

As many have stated they augment the active component. Currently most of the service support components are in the Reserves. Close to 80% of those units have deployed some several times over the years to support the Active component.

To expand some on what MSgt Robert "Rock" Aldi said about Air Force Reserve. Some Wings have associate Reserve units. The associate flying squadron flies missions in any of the Wing’s aircraft. The associate support squadrons maintain active duty and reserve aircraft. It worked well when I was on active duty.

To kick ass and sleep til noon

For when you run low on cannon fodder

they are there to provide logistical support to active component in case a conflict arises. that's how I see it.