On 16 June 1940, the USSR issued an ultimatum to Latvia, demanding the resignation of Kārlis Ulmanis’s government, the formation of a Moscow-loyal government, and the unrestricted entry of additional Red Army forces. That same evening, in a militarily and diplomatically isolated situation, the Cabinet accepted the demands. The next morning Soviet troops crossed Latvia’s border, and the decision of 16 June became the direct prelude to Latvia’s occupation and annexation.

The ultimatum followed the Molotov–Ribbentrop Pact, which placed the Baltic states within the Soviet sphere of influence. Latvia’s state institutions still formally existed, but on 16–17 June their ability to act was broken by military pressure and threats.