In 1917, a series of medieval tunnels beneath the city, linked and greatly expanded by the New Zealand Tunnelling Company, became a decisive factor in the British forces holding the city - particularly during that year's Battle of Arras. thumb|The nearby Canadian National Vimy Memorial By the end of World War I (1918), the city was so heavily damaged that three-quarters had to be rebuilt. The reconstruction was extremely costly, yet it proved to be a success and allowed the city to expand.
In 1917, a series of medieval tunnels beneath the city, linked and greatly expanded by the New Zealand Tunnelling Company, became a decisive factor in the British forces holding the city - particularly during that year's Battle of Arras thumb|The nearby Canadian National Vimy Memorial By the end of World War I (1918), the city was so heavily damaged that three-quarters had to be rebuilt. The reconstruction was extremely costly, yet it proved to be a success and allowed the city to expand.