Semper Mars: Book One of the Heritage Trilogy is a military science fiction novel by American writer Ian Douglas.

At the same time UN forces capture the International Space Station, to control any and all launches to Mars, while the UN leadership increases diplomatic pressure on the American government.

The United States finds itself under bombardment from cruise missiles launched from Cuba as well as French, German and Manchurian arsenal ships.

Back on Mars, the Marines are able to escape their imprisonment, but are forced to march across hundreds of miles of Martian desert to reach the UN base.

The CNN review called the novel "well researched, and quite imaginative" with "compelling battle sequences" and also at times even evoking "sentimental pride for the USMC.

"[1] On SFRevu, Ernest Lilley said the novel was similar to a Tom Clancy techno-thriller with its well constructed and plausible world political situation.

Though praising Douglas for his depiction of extraterrestrial combat he found it disappointing that the alien artifacts had such a low profile.