The other big historical anniversary right now is the Great War. And what happened 100 years ago today needs to be mentioned. On April 22, 1915, the Second Battle of Ypres began - it was a very important battle, because it marked the first successful use of poison gas in WWI. The Germans opened the attack by releasing a great mass of chlorine gas - they had it in canisters that they opened by hand, and hoped the wind would carry it over the French lines. It did (though it also poisoned a good number of Germans) - it devastated the soldiers in the front lines, and caused a huge gap to open in the lines. But the Germans weren't prepared to exploit the opening - they didn't have reserves ready to attack, whether because they didn't think the gas would work that well, or because they were as afraid of it as the French, I don't know. In any case, the hole opened, but by the time the Germans attacked, the Allies were able to close the gap. And just like that, they were back to regular trench warfare, and the battle continued another month and another 100,000 or so casualties for both sides.
On a tactical level, it was WWI in miniature - a new method of attack that did, in fact, break the stalemate, but that couldn't be exploited, followed by endless repetitions of the same tactic, that couldn't work again. Almost from the start, certain Canadians realized they could protect themselves from the gas by pissing on cloth and breathing through it - it didn't take long for word to get around, and then for gas masks to be distributed. These defenses were never enough to prevent the horrors of gas warfare, but they were enough to negate it as an offensive tactic. It just became another horrible way to die. And everyone kept doing it - the Germans tried again on the 24th of April, with some success, but never enough to break through. After that, everyone started using gas, but it was never decisive again. Just another method of killing, that usually caused as much trouble for the attackers as the defenders (since the gas hangs around in trenches, and you have to advance through it). It is one of the many things that made this war one of the most horrifying things human beings have done to one another, made trench warfare a sustained hell on earth. And, after April 22, 1915, never really accomplishing anything of military importance.