The declaration of war by Germany on Romania was a critical moment in World War I, highlighting the shifting alliances and strategic objectives of the Central Powers. Romania, seeking to expand its territory and secure its national interests, had joined the Entente Powers in late 1916, enticed by the promise of territorial gains in Transylvania and Bessarabia. This move was perceived as a direct threat by the Central Powers, particularly Germany and Austria-Hungary, who had strategic interests in the region.

Upon declaring war, Germany mobilized its troops to carry out a military campaign aimed at subduing Romanian forces. The German High Command recognized the importance of Romania's resources, especially its oil fields at Ploiești, which were vital for fueling the war machinery of the Central Powers. As the Eastern Front continued to experience wear and tear, the annexation of Romanian resources became increasingly pertinent.

The declaration shifted the dynamic of warfare in Eastern Europe, forcing Romania to defend itself against an organized and superior military force. The German assault was marked by quick and decisive operations, utilizing superior strategy and logistics. This campaign not only fed into the broader conflict of World War I but also underscored the importance of alliances and resource control in multinational warfare. Furthermore, the outcome of the conflict had lasting ramifications on Romania's territorial integrity and political landscapes in the post-war era.