In 1939, Britain and France declared war on Germany and the war began. Or did it? After the German army had overrun Poland it did not seem that there was war in Europe. And so the Phony War began.
After the Battle of Poland neither Britain nor France were ready to begin advancing in Europe. The French had the larger of the two armies, and they were not about to advance up to the German border. In actual fact, it was the Maginot Line where a good portion of the French army would be stationed. Consolidating the Maginot Line was a primary military consideration for France.
Britain did not have any notable fronts during the phony period. The Italians were not yet in the war during this period, so the North Africa front did not open until after they invaded Egypt in 1940. The RAF did not begin any notable bombing raids during the period either, even though they had suitable aircraft and bombs for more extensive aerial operations.
However, at sea there were some naval skirmishes and battles. Among the first of these was the Battle of River Plate. The German navy deployed the pocket battleship the Graf Spee on a commerce raiding mission in 1939 as the Battle of the Atlantic began, so three Royal Navy cruisers intercepted the ship at the battle. During this battle no ships were lost, although the Graf Spee was hit and made for the port of Montevideo. However, as it could not remain in the port the captain scuttled the ship when it left the harbor.
Britain celebrated victory after the battle, and it was one moment in the Phony War that there was actually a battle of some description! Still, the Phony War had not necessarily ended.
In Eastern Europe the USSR remained neutral. The Nazi-Soviet Pact remained firmly intact. As such, it did not seem that Britain or France could count on the Soviets.
However, while the USSR may have remained out of the war with Germany, the Red Army began its war in Finland during 1939. So it was in Finland that some of the most notable military action emerged as Finland's troops halted the Red Army's advance. Hundreds of thousands of Russian soldiers were lost before Finland effectively surrendered later in 1940.
Beyond Europe, the war in the Pacific had not really began. Although the Japanese were at war with China, the USA remained isolationist. In 1940, the American economic embargo began to have more impact; but the war in the Pacific did not start until Japanese bombers struck at the U.S. naval base at Pearl Harbor in late 1941.
The phony period of war did not really end until the Allies began landing troops in Norway for the Norwegian Campaign in 1940. Only then were the British and French armies, along with naval and air support, mobilized for a military campaign in Scandinavia which would ultimately end in defeat. The objective of cutting off German iron ore supplies in Sweden was not fulfilled, but the Phony War had certainly ended as the German army began to move into the Ardennes for an advance into France.
The war in Western Europe only really started when the campaign in Norway began in 1940. Despite the wars in Poland and Finland, the front in the East only truly opened in 1941 after the demise of the Nazi-Soviet Pact. Then the Pacific front expanded months later after Japan declared war on the United States. As such, only the Phony War began in 1939.