Correction, Thursday, 8:09 a.m.: A Syrian-American reader points out that “zero hour” on Twitter refers to a future planned protest, not the ceasefire. This version has been corrected.

There was no sign of the planned withdrawal from cities and towns by Syrian forces Tuesday.

Smoke rises following purported shelling in Homs, Syria, in an image accessed Tuesday. (Syrian Media Council/AP)

“A successful overthrow of the regime needs more muscle than social media can supply,” writes David Blair at the Telegraph.

He may be right.

Despite support on Twitter, YouTube and blogs for Syria’s “zero hour” — a term activists adopted to describe a planned mass demonstration in Syrian cities — there was no cease-fire at all.

There was no cease-fire despite the posting of YouTube videos in which alleged witnesses tell of horrific killings in Syria, in which a young boy is shown being graphically tortured by the Syrian regime, and in which activists document what they say are the daily horrors in Homs.

There was no cease-fire despite the creation of a Facebook page to protest the detainment of a woman known only as “Rima,” who was reportedly arrested Monday after she held a banner in front of Syrian parliament that read: “Stop the killing. We want to build a country for all Syrians.”

And there was no cease-fire despite a spike in Syrian users of the Tor network, an open network that helps people (often activists) avoid surveillance online.

“The 13 months of Syria’s revolt have starkly illustrated the limits of social media as an engine of revolution, and of the claims made for the internet’s transformative power,” writes Blair.

Information shared by citizen journalists have galvanized international support. But as the continued fighting illustrates, that international support has yet to stop the violence.

World leaders have ramped up the pressure. The Associated Press reports that U.N.-Arab League Special Envoy Kofi Annan announced that the Syrian violence must end with “no preconditions.” That means a cease-fire must really be a cease-fire.

But it is unclear what it will take to get there.