They renewed their acquaintance during World War I, when in 1917 they reported for basic training at Fort Sill, near Lawton, Oklahoma, with a unit of soldiers from the Kansas City area.
Jacobson spent the rest of his career as a traveling salesman, which enabled him periodically to visit Truman in Washington.
When Jacobson first heard about what was happening to the Jews in Germany before and during World War II, he took to discussing it with Truman.
After he heard the post-war reports regarding the Holocaust and its survivors, his talks with Truman about how to help the Jewish people became more intense.
On March 13, 1948, Jacobson visited Truman at the White House, and persuaded him to meet with Zionist leader Dr. Chaim Weizmann.
Jacobson rejected the suggestion, saying that it was just "a silly dream of a very emotional rabbi", and that he was "too proud of my American citizenship to trade it for any office in the world.