Why did Sauron need ring?

[TheOrcWithNoName]

I am surrpised Sauron trusted Saruman so much when the latter decided to side with him in their search for the Ring.

As has been commented before, Sauron never entertained the idea the Ring would ever be destroyed by mere mortals. What he did fear was someone finding & using their Ring and thus quite possibly usurping his power & position of dominance.

So he may have feared the elves, dwarves & the Men of Numenor. But what of the other wizards, especially Saruman, who had now turned his back on doing good and wanted the share of the spoils over a ravaged Middle Earth.

Surely Sauron must have considered the possibility that Saruman's own armies could have found the Ring before his own, during their tenuous partnership of the two towers.

Saruman owning the Ring would have completely overwhelmed the Dark Lord and Mordor would have been crushed by the might of Isengard & Orthanc.

So I am quite surprised Sauron placed so much trust in the alliance with Saruman, even though as we later know Saruman failed quite miserably at Helms Deep and on his own doorstep with the revenge of the Ents.