Much is made of the role artillery played in WWI and the wars of several centuries before that, but how did artillery develop to fit in battlefields of WWII, particularly on the European western front?
Specifically, how did it cope with what seems to be smaller and faster moving units than were seen in previous conflicts, along with greater employment of tanks and airplanes which had seen advancements of their own? What technical innovations, if any, for artillery were involved?
In WWII artillery kept it's important tactical role from the first world war. Artillery compensated for the faster WWII tactics by itself becoming faster and more agile. Perhaps the speed of artillery drove more sophisticated WWII tactics, rather than being purely a reaction to new tank and infantry tactics.
The major innovation in WWI was indirect fire. This allowed guns to suppress the infantry from far enough away that a few guns could provide immense firepower to a wide area. However, WWI indirect fire worked less and less well as the infantry changed position, especially moved forward, because Artillery could not obtain good targeting information in a timely manner for a target that could not be seen by the battery itself, and systems of communication were weak.
By the Second World War, these problems had been considered by tacticians and various ways of addressing the problem of finding targets for indirect fire had been worked out by each army. Generally, these involved the use of Forward Observers amongst the infantry, as well as special maps and procedures designed to get information about where to shoot back to the artillery batteries as quickly as possible. There are a few hobbist/wargamer articles about this floating around the 'net and [here's one that sites sources] (http://balagan.info/artillery-and-mortar-tactics-of-ww2).
The net effect of all the above was that during WWII Infantry rarely lost touch with their artillery support, which had stalled many WWI offensives.
Additionally, motorized transportation helped the mobility and firepower of artillery nearly as much as the armored units. Armies were able to tow their artillery pieces behind trucks, or mount them on a tank chassis as "self-propelled artillery." Motorized logistics meant that ammunition could keep pace with batteries and allow units to sustain firepower during offensives. For some armies, the radios that made Armored units and airpower so effective also enhanced the ability of infantry units (and armor, and spotter aircraft) to call in quick and accurate artillery fire.
It's important to remember that WWII armored units were not just, in Churchill's 1940 phase "the onrush of a few thousand armored vehicles" but included both infantry, artillery, and unarmored vehicles coordinated by radio. Tanks themselves were not invulnerable to artillery fire. Direct hits, (usually lucky hits due to indirect fire, but artillery could also shoot in a direct fire role) could knock out tanks and near misses damage their treads and mobility. Tanks would be forced to "button up" by artillery, restricting their visibility and thus firepower. The supporting infantry of an armored formation would also be suppressed, greatly restricting it's ability to deal with enemy infantry in close combat.
It's worth noting that the ratio of artillery firepower to infantry units was actually higher in most WWII units than it had been in the previous war. While the Tank and Airpower were more obvious innovations, the Artillery had not ceased to improve.
I'm no expert but I currently serve in the RA so hopefully this may help.
WWII was a dynamic war with the opposing sides looking to quickly take exploit any weaknesses. British manoeuvre warfare tactics have and still are a very simple mantra:
To this day this still remains the main tactical aim when tasked with clearing an AO.
Artillery allows you to achieve many effects on the enemy in order to complete this cycle:
With improved communication and indirect firing principles artillery was able to called in faster and more accurately.
A big advancement in the Royal Artillery was the concept of the FOO (Forward Observation Officer), usually a junior captain capable of developing what was known as a Foo's fire plan. In this he would de-conflict the fire of various assets including Close Air Support, Artillery, Mortars, Naval fire etc in order to create a fire plan to support an operation (usually at company level). In this way the FOO was given a lot of freedom to conduct his fire plan as he was the best equipped an usually best informed due to his forward position.
Anti-armour fire was rarely used defensively however could be used to DISLOCATE or DISRUPT enemy armoured units with it's main priority being destroying C2 and Logistic support nodules to render armour ineffective.