Between 1850 and 1871 the [[Fort Monostor]] (<em>Monostori Erőd</em>) was built nearby.
In 19191918, Komáromthe wasArmistice treaty drew a demarcation line that split Komárom in two by the newly created border of [[Czechoslovakia]]. This split was by 1919 made ''de facto'' by the arrival of Czechoslovak troops. In 1920 Hungary was forced to sign the [[Treaty of Trianon]] recognizing the new imposed borders including the border with Czechoslovakia. The loss of its territory created a sizable [[Hungarians in Slovakia|Hungarian minority in Slovakia]]. The Slovak part is today [[Komárno]], [[Slovakia]]. In 1938 the entire city was returned to Hungary, its Regent, [[Miklós Horthy|Admiral Horthy]] receiving a tumultuous welcome from the citizens as he crossed the old bridge and entered the formerly dismembered part.<ref>{{cite AV media|url-status = dead|url = https://www.youtube.com/watch?v=hs1NjePbPho|title = YouTube, a Google company|website = [[YouTube]]|access-date = 2018-03-05|archive-date = 2019-06-10|archive-url = https://web.archive.org/web/20190610174719/https://www.youtube.com/watch?v=hs1NjePbPho}}</ref> At the end of [[World War II]] the city was again divided between Hungary and Czechoslovakia.
After World War II the occupying Soviets built the country's biggest ammunition storage in the Fortress of Monostor. Thousands of wagons of ammunition were forwarded from this strictly guarded area. One of a series of forts, the Monostor is today open to the public as a museum.
