Liepona is a small rivulet that flows for 22.9 km (14.2 mi) on the border of Lithuania

Lithuania

Lithuania , officially the Republic of Lithuania is a country in Northern Europe, the biggest of the three Baltic states. It is situated along the southeastern shore of the Baltic Sea, whereby to the west lie Sweden and Denmark...

 – Kaliningrad Oblast

Kaliningrad Oblast

Kaliningrad Oblast is a federal subject of Russia situated on the Baltic coast. It has a population of The oblast forms the westernmost part of the Russian Federation, but it has no land connection to the rest of Russia. Since its creation it has been an exclave of the Russian SFSR and then the...

, Russia. Left tributary to Širvinta, Liepona originates in Lithuania, near Kylininkai village. In 1980, a 26 hectares (64.2 acre) pond for irrigation was built about 16 km (9.9 mi) from the mouth.

It is famous for an incident in June 1940 when President of Lithuania Antanas Smetona

Antanas Smetona

Antanas Smetona was one of the most important Lithuanian political figures between World War I and World War II. He served as the first President of Lithuania from April 4, 1919 to June 19, 1920. He again served as the last President of the country from December 19, 1926 to June 15, 1940, before...

 had to cross the shallow river in order to reach Nazi Germany

Nazi Germany

Nazi Germany , also known as the Third Reich , but officially called German Reich from 1933 to 1943 and Greater German Reich from 26 June 1943 onward, is the name commonly used to refer to the state of Germany from 1933 to 1945, when it was a totalitarian dictatorship ruled by...

 in the aftermath of the Soviet ultimatum to Lithuania

1940 Soviet ultimatum to Lithuania

The Soviet Union issued an ultimatum to Lithuania before midnight of June 14, 1940. The Soviets, using a formal pretext, demanded to allow an unspecified number of Soviet soldiers to enter the Lithuanian territory and to form a new pro-Soviet government...

. Liepona served as a natural border between Prussia

Prussia

Prussia was a German kingdom and historic state originating out of the Duchy of Prussia and the Margraviate of Brandenburg. For centuries, the House of Hohenzollern ruled Prussia, successfully expanding its size by way of an unusually well-organized and effective army. Prussia shaped the history...

 and Lithuania since the Treaty of Melno

Treaty of Melno

The Treaty of Melno or Treaty of Lake Melno was a peace treaty ending the Gollub War. It was signed on September 27, 1422, between the Teutonic Knights and an alliance of the Kingdom of Poland and the Grand Duchy of Lithuania at Lake Melno , east of Graudenz...

 of 1422 with the Teutonic Knights

Teutonic Knights

The Order of Brothers of the German House of Saint Mary in Jerusalem , commonly the Teutonic Order , is a German medieval military order, in modern times a purely religious Catholic order...

.