The French name for the Belgian town of Ieper, in West Flanders (It is more usual to use Ieper, the locally used Dutch name, for contemporary references in English, but the battle is always referred to as Ypres). After the Western Front settled down, the Westhoek was the sole remaining corner of Belgian territory which had not been occupied by the Germans, and since protecting Belgium was notionally the main reason that Britain had come into the war, it was politically expedient to hold onto it. Inevitably, this meant attempting to defend an awkward salient, largely overlooked by higher ground. Although there were three named battles of Ypres (in 1914 (last ditch heroics and the establishment of the trench lines), 1915 (gas) and 1917 (mud) - the third also known for the village of Passendale or Passchendaele), fighting in the area was more or less continuous for four years, during which time the city itself was, of course, razed to the ground. It has been rebuilt and largely restored as it was (a Belgian habit following wartime destruction), and now lives a quiet life living off linguistic technology, battlefield tourism and a triennial Kattestoet or cat parade, in which the role of cats in history is celebrated and stuffed cats then hurled from the rebuilt Cloth Hall into the crowds below. Its most moving memorial, however, is the Menin Gate with its endless lists of the unlocated dead of the salient, and the surrounding cemeteries, particularly Tyne Cot.
vruba says I should very much like to know how to pronounce Ypres. Ee-pr? Yip-rayz? Ip-ray? Stick it in your writeup and earn eternal gratitude.
The French is roughly "EEP-r" with the r being a barely audible grunt in the back of the throat (a uvular); the word is very close to being a monosyllable. It is thus rather closer than it may appear to the Dutch Ieper, which is roughly EEP-er. The British forces who fought there, however, universally referred to it as "Wipers" (as attested to by the trench journal published there, the Wipers Times).