June was a decisive month in the history of the world wars. During this period, attacks, treaties, and battles occurred that altered the political and military balance of Europe and the world.
From the beginning of World War I to the Normandy landings in World War II, several events that took place in June marked the course of the 20th century.
Both conflicts also left behind deep economic crises, millions of displaced people, destroyed cities, and political changes that transformed the world map for decades.
World War I: key events in June
World War I was one of the most important conflicts of the 20th century.
In June, some fundamental events took place, from the attack that triggered the conflict to the treaty that officially ended the war and redrew the political map of Europe.
Assassination of Archduke Franz Ferdinand of Austria
The assassination of Archduke Franz Ferdinand of Austria in Sarajevo on June 28, 1914, was the immediate trigger for World War I.
The heir to the Austro-Hungarian Empire was assassinated by Gavrilo Princip, a Bosnian Serb nationalist linked to groups seeking the union of South Slavic territories.
The cause of the attack lay in the growing nationalist tension in the Balkans and the rejection of Austro-Hungarian control over Bosnia.
Following the assassination, Austria-Hungary blamed Serbia and launched an ultimatum that activated the European alliance system. Within a few weeks, the major powers were at war.
Treaty of Versailles
Five years after the Sarajevo attack, on June 28, 1919, the Treaty of Versailles officially ended the war. It was signed at the Palace of Versailles and held Germany responsible for the conflict.
The treaty arose from the need to reorganize Europe after millions of deaths and the collapse of several empires.
Its consequences were profound: Germany lost territory, was subjected to heavy economic reparations, and saw its military capacity limited—conditions that fueled the discontent that would facilitate the rise of Nazism.
World War II: decisive events in June
World War II concentrated several essential episodes in June, such as invasions, speeches, naval offensives, and landings that marked different stages of the conflict in Europe and the Pacific.
Italy enters World War II
On June 10, 1940, Benito Mussolini declared war on France and the United Kingdom when German victory seemed imminent in Western Europe.
Italy sought to expand its territorial influence and take advantage of Nazi Germany's advance.
Its entry opened a new Mediterranean front and expanded the conflict into North Africa, affecting Allied strategy for years.
Fall of Paris
The occupation of Paris by the German army on June 14, 1940, was the consequence of the rapid offensive known as Blitzkrieg. France failed to contain the German advance following the invasion that began in May.
The fall of the French capital meant the collapse of the French government and the subsequent signing of the armistice.
Germany went on to control much of Western Europe.
Speech by Charles de Gaulle
From London, Charles de Gaulle launched a radio appeal on June 18, 1940, to continue the resistance against Nazi occupation. His message came after the French surrender.
This speech was key because it gave rise to Free France and kept the French resistance alive in exile.
Operation Barbarossa
Operation Barbarossa was the invasion of the Soviet Union by Nazi Germany.
On June 22, 1941, the operation began with the start of the German offensive along the entire Soviet border, as Third Reich troops crossed into Soviet Union territory in one of the largest military invasions in history.
Hitler sought to destroy the Soviet regime and seize strategic resources.
The operation opened the Eastern Front, the bloodiest of the war, and ended up severely weakening the German army.
Battle of Midway
The Battle of Midway began on June 3 and culminated the following day, June 4, with a decisive victory for the United States over Japan.
Japan intended to destroy the U.S. Pacific Fleet, but the deciphering of its communications allowed the United States to anticipate the move.
The Japanese defeat changed the naval balance and halted its expansion.
Normandy Landings
The Normandy Landings, on June 6, 1944, was the largest amphibious operation in history.
Allied forces landed on the coast of Normandy to open a western front against Germany.
The operation allowed for the start of the liberation of France and accelerated the fall of the Third Reich. It was one of the most decisive military events of the 20th century.
