In a previous blog post 18 months ago I described how the IRA in 1920 designed and used an improvised mortar. I’ve now found some context for that development and found out where a damaged mortar tube from 1920 exists today. Some of the below is a repeat of the earlier post and some is new information.
A number of IRA members had fought in the British Army in WW1 and had experienced trench mortars, either as a user or recipient. The IRA funded a secret delegation to visit Germany and buy arms on the black market , including a German trench mortar but this mission was unsuccessful. As a fall-back they asked their engineers to develop a home made mortar based on the British “Stokes” trench mortar. I’m not sure how closely they followed the design, but the IRA version appears to have been of same calibre as the Mk 1 Stokes mortar (3 inch) and projected an 11lb mortar bomb, again the same as a Mk 1 Stokes mortar. It appears that the IRA was able to obtain British Army manual for the Stokes mortar. The tube was made by Matt Furlong’s brother, Joe, at a railway workshop, and Matt (who later died testing a version of the mortar) made the bombs for it at 198 Parnell St, Dublin.
Some early Stokes mortar bombs are “armed” on launch by use of a grenade lever spring which is released when the lever arm is free to fly off as it leaves the barrel. I can’t be certain but i suspect the 1920 IRA mortar bombs used this principle too, and not the more sophisticated fuze design used in later WW1 Stokes mortars. Here’s a British Stokes mortar handbook from 1919 showing the later fuze types. Here’s an image of a Stokes mortar with a fuse fitted with a fly off lever.
The propellant charge was a 12 bore shotgun cartridge with shot removed and more propellant (black powder) added. The impact fuze was adapted from a grenade fuze, (as was the early Stokes mortar bomb fuze). The mortar bomb weighed 11lbs. I don’t have exact details but have a pretty good idea and those of you with an EOD background can probably make the same assumptions about arming on launch as I have. For the rest of you, tough.
The IRA conducted some extensive trials, under Matt Furlong of this improvised mortar system in October 1920 in County Meath. First a number of dummy mortar bombs with propellant only were fired, to establish ranges and calculate the propellant charge needed for a range of 100 yards. Then three bombs were fired without a main charge but with an impact fuze fitted to test initiation. The trials established that the bomb tumbled through the air, but despite that, the fuze appeared to work however it struck the ground. One of the engineers believed that the impact fuze was being initiated on “set back” within the mortar tube and not on impact at the target. This is an important assessment ignored by Matt Furlong. Attempts to fire a “live” mortar failed as the bomb got stuck in the tube. Probably fortunately.
The engineers involved were concerned about the impact fuze functioning on “set back” within the mortar tube, so they added an additional safety mechanism (which I won’t describe here) and this was was built in to the fuze for subsequent trials. The second set of trials took place near Kells in County Meath. After firing a live shell with the new safety feature which then failed to function on impact, an argument ensued between Furlong and McHugh, an assistant who was present. Matt Furlong insisted on removing the additional safety feature and firing the mortar as originally designed. McHugh, nervous, stepped a few yards away. The others retreated. As the mortar bomb was launched it did indeed explode in the tube, severely injuring Matt Furlong, who later died in hospital after losing a limb.
The loss of the mortar was seen as a significant blow to the IRA in Dublin who had expected to be able to mortar barracks with impunity mounting the mortar on the back of a vehicle, a tactic that they applied successfully 60 years later in the North.
The mortar tube that exploded, eventually killing Matt Furlong, was hidden in the River Tolka for some years before being recovered. In 1937 it was given to the National Museum of Ireland (NMI) where it exists today. There’s some pictures at this link here – it has been mounted at an incorrect angle, but that doesn’t matter.
(Note the damaged base of the mortar tube some way down the page)
On occasion the arming system also failed in later IRA mortars, as I can vouch for personally. To me there is a clear technological development route from the Stokes mortar of WW1, to the IRA’s improvised Mk 10 and Mk 11 mortars of the late 1980s and early 1990s. I think there is a distinct possibility that the PIRA designer of the Mk 10 mortar and bomb based the designs in part on the 1920 Joe Furlong designed mortar and bomb which in itself was based on early WW1 Stokes Mortar designs.
Additional research leads me to believe that the additional safety feature in the mortar fuze that Matt Furlong removed before his accident was remarkably similar to a fuze safety feature I saw in on operations in 1991 – on another IRA mortar. That’s seventy years apart, and essentially the same safety feature being used on an improvised mortar. I won’t post details here, of course. The British Army EOD techs of the time were certainly not aware of that provenance. More fool us.