Liberia remained neutral for the first years of World War I, but in 1918 joined the Allied side, and is counted amongst the victors of the war.
Liberia in World War I Wikipedia
Prior to the beginning of World War I, Liberia was largely impoverished and unstable, and dependent on Germany for around 75% of its foreign trade. The start of the war caused a drop in German trade, with resulting severe impacts on the Liberian economy. Although the start of the war globally prevented Liberia from acquiring weapons, the American government consented to sell the Liberians arms at half-price, enabling the Liberian Frontier Force to keep down local insurrections.
In April 1918, Liberia declared war on Germany, and seized German assets in the country, resulting in yet further economic disruption, particularly as German companies had displaced Liberian businesses in the local economy; this was further exacerbated by a German submarine blockade affecting Liberian ship traffic.
Liberia had minimal kinetic involvement in the war itself, with Monrovia suffering one shelling by German submarine in June 1918, and a small number of Liberian troops serving in France, though they did not see combat.
As an Allied nation, Liberia received Liberty Loans from the United States, though this financial support decreased greatly after the end of the war. A loan to "bolster and replace" profits lost as a result of Liberia's involvement was proposed by President Woodrow Wilson, but blocked by the United States Senate.