The Invasion of 1910: with a Full Account of the Siege of London (1906) by William Le Queux and H. W. Wilson
"The Invasion of 1910 is a 1906 novel written mainly by William Le Queux (with H. W. Wilson providing the naval chapters). It is one of the more famous examples of Invasion literature and is an example of pre-World War I Germanophobia, as it preached the need to prepare for war with Germany." Wikipedia
There were many, many stories of this type published in that era as I. F. Clarke made a career of showing. The European nations were itching for WWI. Other notable examples are The War in the Air (1908) by H.G. Wells, "The Swoop!, Or, How Clarence Saved England" (1909) by P. G. Wodehouse, and "The Secret of the Army Aeroplane" (1909) by A. A. Milne, the creator of Winnie-the-Pooh.