The newly independent country faced as many as three major foreign enemies in the years between 1918 and 1921: the Bolsheviks, the pro-czar Bermontian army of former World War 1 POWs led by Pavel Bermont-Avalov and the Republic of Poland, also born at the final stages of the World War 1.
Lithuania withstood the foreign interventions, but the Polish attack in breach of the Suvalkai Treaty led to an annexation of the eastern Lithuania (including the capital city Vilnius) to Poland. This was never recognized and Lithuania remained at a state of war with Poland, with the new government city Kaunas officially designated the “Temporary capital”. “We won’t calm down without Vilnius” became a popular slogan and organizations like the “Union for the Liberation of Vilnius” sprung up with the Lithuanian-Polish territorial dispute becoming one of the keystones of interwar Lithuania’s policy.
The main western powers recognized Lithuania only in 1922 as they preferred a stronger Poland to counter the German and Soviet threats. But by 1922 it was already clear that the Polish-Lithuanian Commonwealth will not be reborn as the Poles ceded many eastern lands to the Soviets in the Treaty of Riga.
Unlike the part of Lithuania that was in the Russian Empire, Lithuania Minor remained under the German rule except for its northernmost part, the Klaipėda Region (German: Memelland), which was detached from Germany due to its Lithuanian majority. As the Lithuanian Republic was still unrecognized, Klaipėda Region remained under League of Nations rule. In 1923 Lithuania supported a revolt in Klaipėda Region and the new directory (government) of Erdmonas Simonaitis joined Lithuania (as a bilingual autonomous area) thereby giving the young country its only seaport. Together with it came a sizeable German minority which caused trouble in the 1930s when the Nazi ideas caught on among the Germans of Klaipėda Region.
1926 saw a military coup and the new president Antanas Smetona ruled until the end of independent Lithuania, with the period thus frequently known as the “Smetonic era”. Lithuania became one of the first authoritarian countries in the Eastern Europe, but by the year 1936 only a few, such as Czechoslovakia, would still remain democratic.
Interwar Lithuania continued to be an agricultural society with only 20% of people living in cities, therefore it was less heavily hit by the Global Depression, remained a devout Catholic land with the church not disestablished and birth rates soaring (the population increased by 22% to over 3 million in years 1923-1939 despite a sizeable emigration primarily to the South America).
The foreign policy of Lithuania was friendly to the Germans and Soviets because of many other countries, like France or Estonia, supporting Poland in the conflict over Vilnius. However, the increasing imperialism of both Germany and the Soviet Union eroded their need for independent Lithuania. In 1939 German ultimatum led to the loss of Klaipėda Region. A secret Molotov-Ribentropp pact protocol included Lithuania in the German zone of influence, but the Smetona’s refusal to invade Poland together with Germany led to the change in the protocol with Lithuania being “ceded” to the Soviet Union. In 1939 Soviet Union established army bases in Lithuania after an ultimatum (this ultimatum also returned 1/5th of Vilnius region, recently occupied by the Soviets during their invasion of Poland), and another ultimatum in 1940 led to a full-scale occupation and annexation.
See also: Top 10 interwar sites in Lithuania