Lithuania–Poland border

One commonwealth, then partition

In 1385 the Lithuanian ruler Jogaila agreed to join his realm with Poland by marrying its young queen, Jadwiga, and taking the Polish throne. On 1 July 1569 a joint parliament at Lublin turned this loose union into a Commonwealth of Two Peoples, with a shared king and parliament, though each kept its own administration, laws and army.^[5]

The Commonwealth was carved up by its neighbours in three partitions, in 1772, 1793 and 1795. Most ethnic Lithuanian land went to Russia, but the area southwest of the Nemunas river went to Prussia and later became part of the Russian-ruled Kingdom of Poland.^[6]

The fight for Vilnius

Lithuania declared independence on 16 February 1918. Its claim rested on Vilnius, the historic capital, but the city was multiethnic with a strongly Polish culture, and many in Poland hoped to revive some form of the old union.^[6] The Polish army took Vilnius from the Red Army in April 1919, and the Western Allies drew a demarcation line that left it in Polish hands.^[6]

In 1920 the two sides met at Suwałki and on 7 October signed an agreement setting a line between their armies, which left Vilnius on the Lithuanian side.^[3][7] On 9 October, the day before it was to take effect, the Polish general Lucjan Żeligowski seized Vilnius in what Poland presented as a mutiny, and proclaimed a “Republic of Central Lithuania”.^[3] Vilnius stayed under Polish control and was formally annexed in 1922.^[6]

“A line of demarcation, which in no way prejudices the territorial claims of the two Contracting Parties, shall be fixed…”^[7]

A closed border

On 3 February 1923 the League of Nations Council set a provisional line, and on 15 March the Conference of Ambassadors recognised it as the Lithuanian–Polish frontier. Lithuania formally refused to accept the decision.^[3] For fifteen years no traffic or mail crossed the line, and communications stayed cut.^[3]

After a Lithuanian sentry shot a Polish border guard on 7 March 1938, Poland sent an ultimatum on 17 March demanding diplomatic relations and restored transport and communications. Lithuania gave in, saying it was yielding to force.^[3][6]

In October 1939, after the Soviet invasion of Poland, the Soviet Union forced a mutual-assistance treaty on Lithuania and in return handed it Vilnius and the surrounding area. In June 1940 the Soviet Union occupied Lithuania, and in August declared it a Soviet republic.^[8]

Neighbours in the EU

Lithuania restored its independence in 1990, secured in August 1991.^[9] Presidents Algirdas Brazauskas and Lech Wałęsa signed a treaty on friendly relations and good-neighbourly cooperation in Vilnius on 26 April 1994. It also set out the rights of the Polish minority in Lithuania and the Lithuanian minority in Poland.^[4]

Both countries joined the EU in 2004.^[9][2] When Poland entered the Schengen Area in 2007, the Berżniki–Kapčiamiestis border crossing, opened only the year before, stopped operating.^[2] Today the border is 104.28 km long.^[1]