Sharpe Battles, in episodic fashion.

Immersion: Combat, and to a lesser extent lets call it, time period because the game doesnt have a set story, just a series of events to play through.
Difficulty: As with any strategy game there is a learning curve built in. Different units have different stats, and so forth to learn. The interface works well enough, and doesnt overly contribute.
Lasting Appeal: Difficult to say, this is where the lack of a sense of progression lets the game down. Battles are discrete tactical puzzles, and while there is a sense of accomplishment in progressing to the next battle, it doesnt have an effect on a map or in a narrative. Its something the series is lacking, in my personal opinion.
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CAP198462 about Peninsular War Battles Gold