The Netherlands stayed neutral in the First World War, but the Dutch government maintained a standing army on the Dutch coast to prevent potential invasions from England. In 1918, an unsuccessful socialist revolution took place in The Hague headed by Troelstra, an MP who wanted to establish a socialist republic. During this time, the powerful monarchies Russia, Germany and Austria had disintegrated, and there were indications that this could happen also in the Netherlands. The revolution was followed by a mass demonstration of supporters of the monarchy in The Hague.

The Second World War had far more disastrous consequences for The Hague. The Netherlands hoped to remain neutral again, but Germany attacked the country in 1940. The Dutch still relied on water as a mean of blocking foreign entry, but the Germans simply flew over the country. There were four airfields around The Hague, and the Germans captured all of them on the very first day of war. Later, The Hague was retaken, and the Queen and the government, whose members had been held hostage, escaped. Many German planes were destroyed and the Nazis retaliated by incessantly bombing Rotterdam, and threatened to do the same to The Hague if the Netherlands didn't capitulate. The country did not have sufficient air defenses and soon surrendered.

Both the Germans and the Allies did extensive damage to the city. The Germans destroyed many 19th- Century buildings near the Scheveningen. Many houses and forest areas were bombed beyond recognition, as well as the zoo, built in 1863. In March 1945, the Allies accidentally bombed the 19th-Century Bezuidenhout, as well as some 17th-Century buildings, such as the elegant American and French embassies.

The Hague’s population increased significantly after the war, largely due to the Dutch colonies of Indonesia and Suriname becoming independent people, consequently arriving in the Netherlands. The Old Town of The Hague today has very few canals left, but still attracts tourists with multicultural festivals and annual events commemorating historical dates, such as April 30, when the Dutch celebrate Queen's Day in memory of their former queen Juliana. There is also a free open-air festival, Parkpop, held since 1981 on the last Sunday in June, attracting some 350,000 fans.