Anne wrote this entry in her diary in February 1944. They had been hearing radio news reports that the Allied troops were getting closer to invading Europe. The people believed that any day that the Nazis would be defeated and Europe would be liberated. The Allies did invade Europe in June 1944 in the famous Normandy invasion. However, Holland, where Anne and her family lived, was not liberated until March 1945. The Franks and the other people hiding in the attic were discovered in August 1944 and were sent to concentration camps. Anne and Margot died in March 1945 at Bergen-Belsen, just days before the camp was liberated. Their father was the only one of their group to survive.
Find the phrase, "Invasion fever is mounting daily throughout the country". The "fever" is part of the building plot. Characters all know well what is meant, so they don't need to tell you outright; If the reader is getting involved in the story, an understanding of the phrase should become a part of the understanding of what the people were going through all over the country at the time. Ask yourself what is going on when the phrase comes up; what were the surrounding paragraphs talking about? What occurs in the plot shortly after the phrase appears? If you look, feel & absorb, rather than simply allowing the words to pass before your eyes, (all of us do that sometimes), you'll discover the meaning in a deeper personal way. The simple answer is the excitement of "short timers syndrome" or "ants in your pants"; waiting for the last class bell or that painful last few days at work before vacation begins & you just don't care about the quality of your job performance right now. In those situations people often become over excited & filled with hope to the point of carelessness. In the book, cautious guard is lowered because the end must surely be near, causing people to do & feel things they might not do or feel if they didn't know a saving invasion might be coming. Invasion fever may have led to the capture of the characters in the end; an important focus point, or moral, of the story.