My Grandpa served in WWII in a infantry cannon company Cannon Co., 414th Infantry Regiment, 104th Infantry Division). I know he was at one time a section chief (gun crew leader) and later became a platoon sergeant. Basically, from what I've read, each regiment in the infantry division had its own cannon company, and the concept was that these would be faster into action than having to call Division Artillery, etc. I've also read that they were used in more of a direct fire role than as indirect fire artillery.        
 

The cannon companies were armed with the
M3 Howitzer
, a short-barreled 105mm gun originally developed for airborne troops.

Anyone familiar with this concept and can give me more detail about when the cannon company came into being, how they were employed and when/why they were phased out? Is there a modern equivalent or has the role been reassigned/eliminated?

"Believe it came into being in late 1943. In North Africa the US army was fighting WWII with WWI training. There were lessons to be learned. One problem was the trouble a rifle company had in getting artillery fire. A request from a rifle company was sent to battalion HQ. From there the request went to division artillery, where several approvals were required. Their answer was The Cannon Company within an infantry regiment. Under the complete control of the regiment, no other approval required. A short barrel model of the standard artillery 105 mm howitzer was developed - the M3. Each regiment had six M3's, two for each battalion. The battalion CO could call for Cannon company to fire a mission - no further approval was needed. It worked. Once in Germany, the lead rifle company of the 3rd. battalion received small arms fire from a German ambulance. A request for artillery fire went up to division. They refused to fire on a "red cross". The fire mission was given to Cannon company, scratch one Jerry meatwagon, the rifle company continued the advance.

A Cannon company was a "service company". As you no doubt know an infantry regiment (so called "a square regiment) was made up three battalions, each consisting of three rifle companies, plus battalion HQ company (square- four sides). The whole army exists only to support these three rifle companies. A Cannon company was one of these support units."

Thanks for the reading suggestions! I have a copy of the FM, but mine is an old photocopy so perhaps the one at your link will be easier to read The other stuff is new to me - much appreciated.

CharlieR posted a great reply to a GD thread I started on the same subject since this one was quiet for a few days....I'll link it here in case anyone missed it.