We know Syrian and Iraqi militants (many of whom are terrorists by any other name) have been making their own improvised weapons for some time (see here for some examples). However, this home-made improvised cannon on the back of a truck, courtesy of bmashina’s Tumblr page, made me blink.
It reminds me of nothing so much as the muzzle-loading cannon common in European warfare from the Renaissance through the Napoleonic wars, or the early breech-loading cannon that succeeded them. See, for example, this British Ordnance BL 12 pounder 7 cwt breech-loading artillery piece from the 1880’s.
One wonders whether something like the older cannon didn’t serve as a visual inspiration for its home-made modern equivalent (and whether a museum specimen didn’t help the designer of the latter weapon to figure out how to construct it). It looks as if a hydraulic piston from a modern piece of earth-moving or construction equipment was used as a recoil-absorbing mechanism. Ingenious, but a bit frightening if something lets go at the wrong moment!