Curated OER
History Matters: The Zimmerman Telegram Bringing America Closer to War
This is a copy of the actual Zimmerman Telegram where Germany states that it "Intends to begin - unrestricted submarine warfare." A great primary source that takes students deeper into historical understanding.
Digital History
Digital History: The United States Wwi
This site explains how Germany resuming unrestricted submarine warfare contributed to the US entering WWI. Site is well-written, informative, and contains great details.