10 years ago, I read the following quote
A human being should be able to change a diaper, plan an invasion, butcher a hog, conn a ship, design a building, write a sonnet, balance accounts, build a wall, set a bone, comfort the dying, take orders, give orders, cooperate, act alone, solve equations, analyze a new problem, pitch manure, program a computer, cook a tasty meal, fight efficiently, die gallantly. Specialization is for insects.
-- Robert A. Heinlein
I've since learned several of these skills, but I've not yet learned how to plan an invasion. In doing an overview of some well-known invasions (Schlieffen Plan, Operation Barbarossa, Operation Overlord, Operation Iraqi Liberation, etc), it struck me that all of them were planned by large teams of people who brought specialized skills (meteorology, logistics, signals, espionage, etc) to bear. This makes sense and follows what I've learned about leadership, but goes against the core spirit of the quote. If I wanted to take the quote seriously, I'd need to learn to manage all these aspects individually rather than relying on the skills people have gained through a career of study and specialization.
Are there any historical examples of an invasion where the planning was performed entirely by one person who merely had a high level of general competence?
I'm particularly interested in examples of invasions
Where territory was successfully captured and held for at least a year.
Which occurred post-1916.
Which had to oppose the active resistance of a small or medium-size power.