The unfortunate reality is that the posting appeared 4 1/2 years ago, an eon after reliable information became easily found. Where do I start?
First off, I do agree with RichT090 on two points: the Philippine Army went to war ill-equipped, not to mention poorly trained in most instances, and
there were zero 105mm howitzers—barely into production—in the Philippines, although plans existed to send a passel of them out there when available. For the rest of it....
> USA Field Artillery comprised 24 M1916 75mm and possibly 12 M1897 75mm, Philippine and PS field artillery comprised....124 M1916 and M1917 75mm Guns.... >
Much of this history has been covered previously in the forum, but again, the mainstay in the Philippines was the animal-drawn M1917 and the truck-towed M1917A1 75mm field gun (a.k.a. the British 75). Louis Morton’s 1953 The Fall of the Philippines
includes numerous instances of their combat use. Other than the modernized variant on the lately arrived T12 half-tracked SPMs, there were no M1897 fieldpieces in the Philippine or Hawaiian Islands, for the good reason that the Ordnance Department considered its hydropneumatic recuperator too tricky for the local ordnance machine shops to mess with. [I concede this may have been merely an excuse to relegate the non-standard M1917s to insular outposts in the Pacific.] According to a prewar ordnance inventory, there were a total of 14 M1916A1 75mm field guns on the islands, which frankly have remained elusive in both their distribution and deployment. Morton makes no mention of them, but he does provide many instances in which 75mm guns seeing action are unspecified as to model. Alas, I can offer no additional information on the service and fate of these 14 M1916A1s.
> 52 ex-Indian Army 2.95" mountain guns >
Wow! Where did that one come from, Gunga Din? Who knew the U.S. Army was taking hand-me-downs from the Indian Army? IMO, it should have held out for the much better 3.7-inch mountain howitzer. In reality, around 1900, involved in the Philippine Insurrection, and finding the Hotchkiss 1.65-inch mountain gun too small and the Hotchkiss 3-inch mountain gun poorly designed and dangerous to use, the U.S. Army contracted with Vickers-Maxim to acquire 120 of its export 2.95-inch mountain gun (not
a howitzer). The deal was to purchase 30 guns outright at cost, and then to obtain a license to build the other 90 at Watervliet Arsenal. The little brute had a short recoil and loved to jump, but still it served against the Japanese in 1941-42, even managing to knock out a Type 95 Ha-Go light tank during the campaign.
> 36 "3-inch" weapons that otherwise remain unidentified, but which may have been M1902, M1905, or M1906 Guns >
Just to nitpick, the actual models of the early 20th century 3-inch field guns are the lookalike M1902, M1904, and M1905. All have a block trail, with limited elevation, as is typical for most of the light field guns that served in the Great War. By the early 1940s, all of these 3-inch guns had long been relegated to saluting and ceremonial uses. I think there were a small number in the Philippines, at Fort Stotsenburg and other posts, likely on the parade grounds firing as morning and evening guns, but hardly suitable for combat. I suggest the 36 3-inch pieces alluded to may have been antiaircraft guns, mostly mobile M3s, but also a few fixed M1917s (the latter out in the Manila Bay harbor defenses). One of the M3 3-inch AA guns on Corregidor (Battery Boston?) is shown here.
To answer Nuyt’s question, archival documents account for 20 3-inch naval landing guns in the Philippines in 1940: the 14 Mark XI pieces transferred from 16th Naval District to the army and a half-dozen older Mark VIIs, some aspects discussed previously in this thread. Unlike the Mark VIIs intended for the NEI but diverted to Australia, the Mark XIs never enjoyed high-speed conversion. There is no evidence the army also took the Mark VII landing guns stored at Cavite.