So that'd be a downer if the Codex were mostly political stuff, but if it is some combination of useful tactics like Reverse Slope Defense/Steel Rain and useful thought devices like “Engage people with what they expect; it is what they are able to discern and confirms their projections. It settles them into predictable patterns of response, occupying their minds while you wait for the extraordinary moment — that which they cannot anticipate.” then it should still apply just fine, even thousands of years later.