In First World War, Ieper was 4 years at the frontline and totally destroyed. No buildings in Ieper are elder than 80 years, even not the "middle age buildings" who were perfectly repaired. Even now there are a lot of unexploded bombs under the ground. In World War 1, Ieper was the first place where they started "modern" chemical warfare.
In Ieper there's not much to see, except the nature around it and military war graves and the "MENENPOORT" (in English called "Menin Gate"), a big militarist monument of the British "Commonwealth War Graves Commission". It contains the names of 56.000 soldiers from Great Britain and its Empire who were killed in the Ypres Salient between October 1914 and the night of 15th/16th August 1917 and who have no known grave. Every evening at 20h p.m. they play a "Last Post" under this monument. And every year there are triumfal militarist parades that glorify war under this so-called "peace"-monument. Read here some opions of about this war tourism.
If you wanna know some war history of Ieper, you can visit the local "IN FLANDERS FIELDS"-museum at the big square in the center. This official war museum with multimedia tools is interesting if you wanna see the cruelty and absurdity of war. You can visit too the private "HOOGE CRATER" war museum or the more commercial one "HILL 62" in a pub, both in Zillebeke some kilometers a the southside of Ieper.
At the big square you find a little monument too for the Polish soldiers who liberated Ieper in the Second World War.