here for an alien empire and many other posts for the Terran Empire of the Technic History.
SM Stirling's Sir Nigel Loring summarizes the British Empire pithily:
presence of mind;
"'...keeping the bloody Frogs out.'"
-SM Stirling, The Protector's War (New York, 2006), Chapter Eighteen, p. 497.
("Frogs" are the French.) Sir Nigel might perhaps have summarized this anti-French policy as "prevention" or "pre-emption."
Stirling reminds or informs us that horses injured in battles scream and that the historical castles of Britain and Europe would become useful again if history took a different course. Poul Anderson imagines orbital forts like Hell Rock.