This note contains spoilers for the book.

Hubbard started out as a fairly honest pulp fictioneer. This one is quite good, and relatively early—he only shows up in SF starting in about 1935.

For context, it was published the same year as Slan, Gray Lensman (#4), and The Ill-Made Knight. Coincidentally, 1940 is the year under consideration for the Retro Hugos just now.

This has a very modern gritty grimness to it (similar to the "noire" detective novels coming out around then though). The Lieutenant is commanding the remnants of a unit of the British Expeditionary Force that has been stuck in Europe for years. Still nominally under command, they have not been supplied, and can't go home due to quarantine. They're living off the population in enemy territory, and they've been doing it long enough that airplanes and artillery are almost nothing but memories.

The war is identified as a second stage of World War Two.

After The Lieutenant takes over England, there's a big gap where he consolidates his control. Then, helpful Americans arrive. We have overwhelming force, and the Lieutenant sacrifices himself to get a good agreement with the Americans‐though I don't see why he thinks it'll be handled, after he immediately murders their installed leaders.