Commando - The failure to wear underwear. Often expanded to involve standing in circles naked, hitting each other in comical sized boxing gloves. Special Forces - Where the "Special" people get sent. Rangers - Park Wardens.

I'll avoid commando and leave that to the British and Boers. Ranger: Today it's an elite parachute light infantry assault soldier. At different times throughout U.S. history it's meant anything from scout to raider or both; even light cavalryman and frontier peace officers have used the term. Special Forces: Broadly speaking today it's almost synonymous with Special Operations Forces in some circles. Originally in the U.S. it referred to a force founded by Col. Aaron Bank on the OSS mold, not shock troops or raiders. The term is still understood that way within the U.S. Army. Light Infantry: A force that requires each soldier to carry about one hundred pounds of "light weight" equipment. Whenever technology allows for some weight savings by making a particular piece of existing equipment lighter, a new piece of equipment, that no one needed before, is added to bring the weight back up to about one hundred pounds. They ride in LPC's (leather personnel carriers).

It depends a lot on what country you are talking about: Though many of these terms are simply English (barring commandos), English has spread far and wide and mutated with the distance. "Light Infantry" is possibly the easiest and the hardest to define. Easisest because its the oldest AND regular unit, and has some concrete paper-trail to follow. Back in the 1700s each battalion had 10 companies of the line (i.e they stood in a line to fire vollies). The flank companies were "special" because the lines depended upon them to function as intended. The right-most one was the Grenadier Company - the biggest and the strongest men choosen to hurl grenades. The left-most was the Light Infantry Company - the quickest men choosen to scout, skirmish and "turn" the line. In the Seven Year (or French and Indian) War some Light Companies performed so well that it was decided to honor them by making a fully Light Infantry battalion-Regiment. The designation "Light Infantry" has since been a term of some pride. Apart from the original Light Infantry, various other Regiments were awarded the title "LI" - like Highland LI for example. BTW: I couldnt resist this, 8th Bombay Infantry - which had been on campaign for nearly 20 continuous years - was turned into the first full Grenadiers Regiment (101 Bombay Grenadiers)... beating the British First Guards who won it some years later on at Waterloo. Funnily 101st is India's Second Guards now. But thats the easy part. Hard part is an even "quicker" skirmishing unit developed during the Napoleonic Wars: the Rifles. They also performed many of the LI work (and some LI battalion had hardened into more-or-less Line infantry). So now they are also light infantry. In British and Commonwealth units they are distinguised by supposedly having to march at a higher pace than Line Regiments. Now all of this doesnt apply to the Americans at all: they thought that the LI is the "regular" unit, and Line units were by-products of Valley Forge. Thats just the history: current definition is more like longrifle's.

PS: Another relatively random history note, at the Battle of Long Island Brits formed a composite assault-unit of Light Infantry and Grenadier Coys from various battalions. It was a pretty risky thing to do -- if these uber-units made a break-through, it can be a huge morale booster; but if they lost or even suffered a little, the set-back was in more than the field itself. It was a common practise to be repeated in later Colonial Wars {especially in societies that still favoured heroic-combat}... but using it against Americans - Englishmen just a few years back - was pointless.

Thanks guys, your explanation did shed some light on the forces in question. Nonetheless, I am still at a loss as to how what these outfits do differs? For example, who does sabotage (blowing up bridges in enemy territory, etc.), who does raids, who does information collection, etc.?

>>Nonetheless, I am still at a loss as to how what these outfits do differs? For example, who does sabotage (blowing up bridges in enemy territory, etc.), who does raids, who does information collection, etc.? << It's kind of a complicated question that could be given a cookie-cutter sort of answer (unit A does direct action, unit B does foreign internal defense, etc.), but that would not really be accurate. There tends to be a degree of overlap and redundancy in special operations units in nations that maintain more than one SOF unit. So, for instance, who blows up a bridge? Depends on who's available. If the bridge is in a coastal area, perhaps you send SEALs. But maybe you send a scuba-qualified SF ODA instead. Hairsplitting about who's more suited for the job aside, both can do it. If the bridge is heavily defended, you might send Rangers, who are trained to operate in larger formations than other US SOF units (but of course you'd probably just hit it with a smart bomb or three). If you've got an MEU(SOC) sitting of the coast and that's the only force available, you might send their recon component, or just line marines to do the same mission. Information gathering -- could be most anyone. Some SEAL units specialize in strategic reconnaissance. Likewise some SF ODAs. Likewise the Ranger Recon Det in the 75th. Or USMC Force Recon. Or the Long Range Surveillance guys assigned to US Army divisions and corps. CAG (Delta) and SEAL Tm 6/DEVGRU/whatever have subunits that specialize in SR besides their more high profile door-kicking capabilities. It all depends on just how sensitive the mission is, who needs the information, the operating environment, who's available and a whole slew of other variables. Or is your information gathering electronic in nature? If so, that spins off a whole list of other units that might get the call. Et cetera. With the way things evolve over time and tend to get driven by mission requirements, theater level peculiarities and the like, it's pretty difficult to pigeonhole a specific unit with a specific mission set.

Thanks for the info, Horsesoldier!

Wiki gives a very comprehensive article on all thingsSAS (UK). here. Well worth the read to get a flavour of what's involved. http://en.wikipedia.org/wiki/Special_Air_Service

I hadn't thought about wikipedia but after you mentioned it I searched it for light infantry and special forces. Good little articles. It should actually explain things quite well for people who are confused about terms.

Useful articles indeed!