The United States has been builting up it's military power since the beginning of the nation. Till World War I started in August 1914. At first, the United States wanted to remain neutral. But in 1917, a German supmarine sunk American carrier as it was entering England. Many American lives were lost that day, causing an anger to every American's heart. The U.S. government ordered a small mobilization. The United States entered the full scale war when German supply ships tried to enter the San Juan Bay in Puerto Rico. On April 6, 1917, Lt. Teofilo Maexuach, the offier of the Porto Rico Regiment in that day, ordered open fire on the German ships. The United States decleared war that day and entered the World War I. The United States Amry entered the already weakening Germany, and advanced fast. The War was over with in a year, by the surender of the new German government on November 11, 1918.