Lithuania's Independance Act, declared on February 16, 1918 came as a result of World War One, which saw Russia yield to Germany after the Bolshevik Revolution.
Lithuania's neighbours Latvia and Estonia, as well as Ukraine and Belarus also regained their statehood at around the same time.
The maps I have seen of interwar Europe look like this, without an independent Ukraine or Belarus (even called Byelorussia or White Russia): http://users.erols.com/mwhite28/euro1935.htm
> The maps I have seen of interwar Europe look like this, without an independent Ukraine or Belarus <
Correct. They had been absorbed by the USSR shortly after they gained independence, and — rightly or wrongly — they were no longer regarded by the international community as indedpendent countries (at least until the farce of their being granted separate U. N. seats when the latter was formed).
On the contrary, during the interwar period, even the USSR recognized Lativia, Lithuania and Estonia as independent, sovereign nations. Then after the Soviets took them over in 1939, most of the non-communist world still recognized the three Baltic states as independent countries.
What’s more, the USA never treated the Soviet takeover as legally valid, meaning that we considered the Baltics to be fully sovereign, independent countries continuously from 1939 until 1990 — whereas we didn’t give that same status to Ukraine and Belarus until the USSR broke apart in 1991.