[Something that the daemons ate . . .]

Of course, this difficulty assumes that you wish to capture the world more-or-less intact and undamaged . . .

IMTU, the Imperium didn't wish to bother with this when it took Earth at the climax of the Solomani Rim War. By this time - after years of hard-slogging through multiple lines of stubborn resistance - the Imperial Navy was concerned only with teaching the Solomani Confederation a lasting lesson. After the invasion fleet took high orbit, the commanding Admiral simply dropped big rocks on every point where defensive structures and/or troop concentrations had been detected, then asked for unconditional surrender. When the defiant Sollies refused this demand, he resumed dropping rocks until the surviving political leadership (they were down to the Minister of Agriculture by then . . .) eventually changed their tune.

Of course, there was major political blow-back on that. The Admiral was retired in disgrace, while Emperor of the time eventually abdicated in apology. But the planet was essentially desertified . . . and the pre-war "blue marble" world is now refered to as Earth-That-Was . . . :P

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