Why is the zimmerman telegram considered a major cause of the united states entering world war i? it guaranteed the use of german u-boats against the united sates navy. it was proof that russia had been planning an attack on the united states for years. it showed that there was an attempt by germany for mexico to attack the united states. it proved that the german foreign minister, arthur zimmerman, was a spy.

The rise of advertising in the 1920s. i am good with seeing how advertisements shape the roaring twenties and how it developed a new way of life through modern days. but i am not sure what the details of advertising in the 1920s were. if possible can you send me links (preferrably credential links) to sources that maybe show like the first company to start advertising through the radio, how advertising benefits (statistics graphs), etc.