helllo to the people that are leftist , anarchist or etc can you give me books to read and also can some one explain theory to me like why do people say read theory what does that mean : ) please help me I'm new to this . Also who ever helps me the most will be given brainlest thank you

The image below is a poster from world war i: image of poster that shows a hun soldier climbing out of the water. the following message is on the poster, beat back the hun with liberty bonds. public domain what was the main purpose of this poster? to create public distrust of germans to encourage young men to enlist in the army to demonstrate the reason for entering the war to generate financial support for the war effort