Symbolically, the treaty was signed in Vilnius, a city which now serves as the capital of Lithuania but which between the wars was part of Poland. President Algirdas Brazauskas of Lithuania hailed the occasion as 'an important step . . . towards uniting Europe'. His Polish counterpart, Lech Walesa, described it as a 'historic breakthrough (which) is leading us out of the captivity of the past'.
For both countries, uncertainties about the future loom larger than lingering disagreements about their intertwined past. Both are extremely apprehensive about developments in Russia and in particular about the large concentration of troops on their borders in the Russian enclave of Kaliningrad. Both, therefore, want to tie themselves into Nato and West European structures as quickly as possible.
In Vilnius, the hope is that closer ties with Warsaw will catapult Lithuania into the favoured 'Visegrad' group of central European countries - Poland, Hungary, Slovakia and the Czech Republic - in the fast lane towards integration with the West. In Warsaw, the hope is that better relations with Vilnius will boost ties and trade with the Scandinavian states to the north.
Despite strong mutual interest, yesterday's treaty took almost two years to negotiate and was the last to be concluded between post-Communist Poland and a neighbouring state. The main stumbling block was Lithuania's insistence that the treaty contain a condemnation of Poland's 1920 invasion and annexation of a large chunk of the south of the country, including Vilnius, which contains a large ethnic Polish population.
For Lithuanians, who played second fiddle to the Poles in the joint kingdom they shared between the 16th and 18th centuries, memories of the annexation were bitter, and fears of a repeat acute. For the Poles, some of whom still regard Vilnius as a Polish city, such a clause was unthinkable and its inclusion adamantly rejected.
In the treaty signed yesterday, no mention was made of the 1920 annexation. But in addition to both sides renouncing territorial claims on the other, a further clause specified that Vilnius was the capital of Lithuania - and would remain so. The treaty also enshrined the rights of the large ethnic Polish minority in Lithuania and the smaller Lithuanian contingent in Poland.