So there you are with your newly built Airfix 4.5", gun, or newly painted battery of 1/285 siege guns, and you can't find them anywhere in your army lists. And you want that big bombardment to start your offensive. Where are these big guns kept? Or where were they kept in the WW2 period?

From reading and researching through several books over the years. the following seems to be the answer. (Sorry, I haven't kept a bibliography as I went along.) In general the ideal in all armies was to have as many non -divisional guns available as divisional. Most Army lists stop at the divisional level, or lower, as the division is the highest really uniform level of organization. So it is above the division we go. Nations varied as to the amount they kept above the division but the below is a good general guide.

The British

The British stayed pretty close to a 1:1 ratio. Corps would have a minimum of a regiment of reserve artillery. This would include heavy AA (3.7"). heavy guns (4.5", 5.5", and 7.2" gun howitzers) as well as additional 25pd batteries. About half the reserve would be 25pd. batteries. The heavy AA was normally kept in rear areas to guard supply and reserve areas. The 25 pd would be kept in a central reserve, and used either in mass or loaned out to brigades or divisions. In the case of heavy artillery, at least one battalion of 4.5" or 5.5" would be assigned to each brigade and the remainder of the heavies would be kept in a central reserve.

The Germans

The Germans maintained a 2:1 ratio early in the war and 3:2 ratio (Div-nonDiv) later in the war. Heavy artillery was organized in regts, and the non divisional artillery would have field gun its well as heavier pieces of howitzers and guns as well as multiple rocket launchers and heavy AA (they had a 105mm in addition to the 88mm). The Germans kept more artillery at lower levels than the British. One other point, all the artillery in a Pz/Gren Div would be howitzers, for greater mobility.

The USA

Both the field and heavy artillery are organized into battalions. Some of the heavies were organized into regts. Div artillery goes up to 105mm and 155 mm howitzers. The non-div would include these plus 155mm guns, 8" howitzers. (both towed and SP) and possibly rocket launchers. 3" and 90mm AA would be found at Corp level. The US maintained a ratio of about 3:2 (Div-NonDiv).

The USSR

The Russians maintained a 1:1 ratio early in the war, and increased this to 2:3 later in the war. The reserve artillery was organized into battalions, brigades, and divisions, under Corp, Army (the most likely level) or Front control. The reserve formations were frequently moved from front to front as needed. The majority, or at least a great deal of the reserve artillery would be the 122mm howitzer. In addition the 152mm howitzer, 122mm and 152mm guns as well as larger weapons and multiple rocket launchers made up the reserve, or non-divisional artillery. In addition heavy AA would be included. Assume at least as many non divisional guns as division, guns and you should be OK. Late in the war, more non divisional guns. Are the above hard and fast rules? No, but they are a good framework, and allow the use of the largest guns in organized fashion. And how are you to be Monty without a preparatory barrage.