The United States declared war against Spain in April 1898 and was a surprise after a chaotic series of events, to include the sinking of the USS Maine in Havana, Cuba. The country was not prepared. Troops were called to southern areas of the United States and held for training and later transport to Cuba, including the 3rd Infantry which left Fort Snelling in April. The 3rd Infantry Regiment encamped near Mobile, AL until orders came for Cuba. The Regiment disembarked in Cuba in June 1898.
The war was short and sharp, with serious ground combat limited to the American envelopment and siege of the Cuban city of Santiago. In July 1898, the Regiment played a significant part in the Santiago Campaign, enduring tropical heat in woolen uniforms while storming a fortified blockhouse at El Caney that controlled a part of the city’s water supply, followed by three days of more or less continuous shelling in trenches before the city until a ceasefire was signed. After redeploying from Cuba and arriving back in the United States in August, the Regiment was held in quarantine in a camp on Long Island, New York before being allowed to entrain for Minnesota in September 1898. The 3rd Infantry earned the SANTIAGO battle streamer for its role.
On December 10, 1898, negotiations resulted in the Treaty of Paris that ended the War with Spain. In the agreement, Spain ceded Cuba, Puerto Rico and Guam to the United States, and transferred the Philippines to the US for a payment of $20 million. The transfer of the Philippines brought about expectations from Filipino fighters that the US would instantly create an independent Philippine nation. When the US did not, uprisings would send the Old Guard on its next mission as part of the Philippine Insurrection.