The U.S Army only ordered two types of trench periscopes during the war. The first kind was a simple wooden box, painted a lovely shade of olive drab and measuring two inches square and 15 inches in length with two inclined mirrors set at both ends (pictured). This type was manufactured by two companies and well over 100,000 were produced.
The second variety was a mirror that was designed to fixed to the end of a bayonet, "a total of 100,000 of these were delivered before the end of July, 1918 and 50,000 additional ones before November".
(Until we get the title link fixed, you can read the article by clicking here.) The German slide-rule jockeys of World War I burned the midnight oil well into the early hours coming up with this weird steel mask for their sharp-shooters... Click here to learn more about W.W. I snipers. During the spring of 1917 the Germans developed a squadron of large aircraft capable of dropping 660-pound bombs on London -and drop them they did, killing as many as 788 human beings between May of 1917 and May of 1918. The Giant Goltha Bombers conducted these raids primarily at night and utterly terrified the East End of London. Eventually, German losses escalated and the London raids were canceled in favor of Paris and various other French targets. In 1917 this image of a Goltha cockpit appeared in the French press. Click here to read an article about the development of aerial reconnaissance during W.W. I.
This article,"Photography's Notable Part in the War" was written by an active participant in the aerial reconnaissance arm of the Royal Flying Corps, Captain Henry A. Wildon. He reported that both sides in the conflict recognized early on that intelligence gathering by way of camera and aircraft was a real possibility: "Our first airplanes in France were not supplied with photographic equipment. It was not until the beginning of 1915 that the importance of of photography became apparent, and was made possible by improvements in the type and general stability of the airplane." At the time when the Entente powers were first exposed to poisonous gas in the spring of 1915, their respective quartermasters scrambled to secure suitable antidotes and precautionary measures that would save the men in the front line trenches. One of the earliest improvisations was a gauze face mask that covered both mouth and nose, drenched in urine. The attached commercial illustration is from the margins of the French news magazine, L'ILLUSTRATION which depicts one of these earlier attempts.
Click here to see an illustration of the German gas shells.
Clicke here to read more articles about W.W. I gas warfare. During the earliest days of the war the British and Empire armies were seldom issued grenades, but the need for such weaponry became apparent once it was clear to all that trench warfare was going to be the norm. The earliest grenades (improvised by both sides) were simply food tins that were jam-packed with an explosive mixed with nails, glass shards and bits of iron. By 1915 grenade production was in full swing and British historians have estimated that throughout the course of the war on the Western Front, British and Commonwealth forces had used fifteen million hand-grenades. The following article concern a British shrapnel grenade that is of the heavy friction pattern. | 
