During World War II the Allies who were a group of countries that cooperated together to oppose the Axis powers, had the mission to stop German, Japanese, and Italian aggression. At the start of the war on September 1, 1939, the Allies consisted of France, Poland, and the United Kingdom, but within a relatively short period, other countries joined the war effort. By the end of 1941, the war had spread to Russia, much of Europe, Africa, and the Mid-East. In December 1941, the US entered the war when Japan attacked Pearl Harbor. Each title in this series contains photos throughout, and back matter including: an index, further reading lists for books and internet resources, and a timeline. Key Icons appear throughout the books in this series in an effort to encourage library readers to build knowledge, gain awareness, explore possibilities and expand their viewpoints through our content rich non-fiction books. Key Icons in this series are as follows: Words to Understand are shown at the front of each chapter with definitions. These words are set in boldfaced type in that chapter, so that readers are able to reference back to the definitions—building their vocabulary and enhancing their reading comprehension. Sidebars are highlighted graphics with content rich material within that allows readers to build knowledge and broaden their perspectives by weaving together additional information to provide realistic and holistic perspectives. Educational Videos are offered at the end of each book through the use of a QR code, that when scanned, takes the student to an online video showing a video relating to World War II. This gives the readers additional content to supplement the text. Text Dependent Questions are placed at the end of each chapter. They challenge the reader's comprehension of the chapter they have just read, while sending the reader back to the text for more careful attention to the evidence presented there. Research Projects are provided at the end of each chapter as well and provide readers with suggestions for projects that encourage deeper research and analysis.