The Great Martian War 1913 - 1917 (2013)

From imdb:

On the eve of the one hundredth anniversary of the beginning of WWI, this mockumentary - employing "archival footage", and interviews with "historians", "researchers" and those directly involved - tells of the Great Martian War (1913-1917), which supplants what looked to have been an imminent great war between Germany and the rest of Europe. The Germans asked their adversaries for help when the Martians invaded Earth via a remote field in southern Germany. The Martians went on the attack first in Germany, then moved west throughout the rest of continental Europe, with the ultimate threat of crossing the channel into Britain. The Martians also took their fight into the waters around Europe. They employed animal-like machines in their battles, the human race which coined the respective machines as "herons", "lice" and "spiders" most closely resembling such animals, each which had their own seeming purpose in the war. The presentation of the ebbs and flows in the human defensive against the Martians discuss what, in hindsight, looked often to be the Martians' luring humans into a longer term goal. Ultimately, the war officially ended when human discovered what was an Achilles heel in the Martian offensive, but ultimately not without great consequence to the human race. Researchers in present day still study the war, with one such researcher, Lawrence Mark, examining the recently found diary of Canadian First Nations soldier Gus Lafonde by his great-granddaughter, Kim Lafonde, most specifically with regard to some Martian code which Mark, in using the code to decipher Martian writing from the time, posits that the Martians had a greater plan than what was initially thought.
—Huggo