I'm running a "Lost Years" era campaign and I've got a Gorn attack on the Federation based roughly on the Japanese attack on the British Far Eastern colonies. The basic idea is a radical faction of the Gorn Confederation attacks a remote section of the Gorn-Federation border and seizes several planets before the outnumbered Federation border squadron can react. The Gorns hunker down and try to make retaking the captured territory so difficult to recapture that the "weak" Federation will sue for peace giving the Gorns the best planets that they captured during the initial invasion. This strategy is very similar to the Japanese plans during the onset of WW2.
"For to win 100 victories in 100 battles is not the acme of skill. To subdue the enemy without fighting is the acme of skill." Sun Tzu - The Art of War