Why not send in ten fleets of D'deridex-Class warbirds and have them surround the planet. Then at a specified time, have them decloak, take out the planetary defences and subspace communications, whilst beaming down thousands of troops to seize the planetary government and neutralise Starfleet's presence.
Vulcan could have been theirs in a matter of hours.
Commander Austin Harris, First Officer, Deep Space Nine (by FltCpt. Bossco)
8.01 - Darkest Before Dawn
(Chapter 8 added, 12/09/2015)