How does Shelley present ideas about power in "Ozymandias"?

Percy Bysshe Shelley presents several ideas about power in his poem 'Ozymandias', the primary one being that power (no matter how strong) is fleeting. Shelley does this largely through the imagery used in the poem; as the poem progresses, the images become more and more focused on the depiction of a once-powerful and intimidating ruler now crumbled in a desert wasteland.

Shelley presents this idea of the loss of power even before the poem's speaker makes it clear that he is describing a former ruler:

"Two vast and trunkless legs of stone/Stand in the desert..."

This image of two stone legs standing without a body already brings in the notion of what was once whole now being destroyed. It is also an immediate image of powerlessness because legs have no power without a body; the body is the source of power.

The description of the statue and its inscription bring in a more focused image of the loss of power:

"Near them, on the sand,/Half sunk a shattered visage lies, whose frown,/And wrinkled lip, and sneer of cold command/Tell that its sculptor well those passions read/Which yet survive, stamped on these lifeless things..."

The fallen body of the statue - the source of power - is described as "half sunk" and "shattered". Not only has the body been dismembered, but it is being further broken down; it is a complete destruction of what was once whole. The description of the statue's face shows shows coldness and cruelty - the primary characteristics embodied by this ruler. And while these characteristics "survive", they survive because they are "stamped on lifeless things"; this is really not survival at all.

"And on the pedestal, these words appear:/My name is Ozymandias, King of Kings;/Look on my Works, ye Mighty, and despair!"

This inscription finally reveals that the statue is one of a ruler and a great one at that. He is compared to God: he is the "King of Kings", which is a description usually attributed to God. He even seems to address God by using the phrase "ye Mighty". The capitalization of "Mighty" echoes the use of "Almighty" when referring to God. Ozymandias even goes so far as to command "ye Mighty" - likely God and other mighty rulers - to "look on [his] Works...and despair!" He believes his power to be so absolute as to be a match to the power of God.

The juxtaposition of this absolute power with the depiction of the desert landscape at the end of the poem fully realizes Shelley's idea about the impermanence of power:

"Nothing beside remains. Round the decay/Of that colossal Wreck, boundless and bare/The lone and level sands stretch far away."

For all of the power this ruler had, nothing remains aside from these words on a lifeless piece of stone and the "boundless and bare" sand. The desert landscape underscores the impermanence of power - and life itself - as it alludes to the Bible passage found in Genesis:

"For you are dust, and to dust you shall return."

This depiction of the impermanence and fleeting nature of power and rulers themselves is likely related to Shelley's own thoughts and experiences during the French Revolution. As David Mikics points out, the image of these ancient ruins actually made its way to Europe after Napoleon's conquest of Egypt in 1798. It is not difficult to see the connection Shelley was attempting to make between the image of this fallen ruler and the trajectory of the life and career of Napoleon and other French rulers.