Why did Latvia have to allow Soviet military bases on its territory in 1939?

In 1939, Latvia was compelled to allow Soviet military bases on its territory due to the geopolitical consequences of the German-Soviet Nonaggression Pact. A secret protocol within this pact assigned Latvia and Estonia to the Soviet sphere of influence, effectively deciding their fate before the outbreak of World War II.123

In early October 1939, the Soviet Union demanded that the Baltic states sign "mutual assistance" treaties. Isolated and recognizing the futility of military resistance against the U.S.S.R., the Latvian government signed the dictated treaty. This agreement granted the Soviet Union the right to establish military, naval, and air bases on Latvian soil, with the stationed garrisons ultimately exceeding the size of Latvia's own peacetime army. This forced concession served as a precursor to the full Soviet occupation and annexation of the country in 1940.4123