World War I was caused by a complex mix of long-term and short-term factors, often summarized by the acronym M.A.I.N.: Militarism, Alliances, Imperialism, and Nationalism. The assassination of Archduke Franz Ferdinand of Austria-Hungary on June 28, 1914, was the immediate trigger that ignited the conflict by setting off a chain reaction through the system of alliances. 

World War I propaganda was a mass media campaign used by governments to shape public opinion by recruiting soldiers, financing the war effort, and demonizing the enemy. Common tactics included powerful posters that used direct calls to action, appeals to duty and courage, and often dehumanized the enemy. Films were also used to present a sanitized or exaggerated view of the war and reinforce patriotic sentiment. 

What makes an entire country take self destructive decisions of eating unhealthy, smoking cigarettes & going to war? Sustained consumption of propaganda! In America, Edward Bernays, a wily young man mastered the art of controlling public opinion via advertising, films & other tools. He relabeled propaganda as public relations & helped the US government & corporates manufacture consent!

The United States entered World War I on April 6, 1917, after initially declaring neutrality in 1914. This shift was primarily due to Germany's resumption of unrestricted submarine warfare and the interception of the Zimmerman Telegram, which revealed Germany's plan to ally with Mexico against the U.S