"If you threaten them and your threat is not credible, it's only going to undermine whatever your policy toward them is. And that could be a logical conclusion from what's just happened," said North Korea expert Joel Wit at the 38 North monitoring group, run by Johns Hopkins University's School of Advanced International Studies.
The US military initially said in a statement dated April 10 that Admiral Harry Harris, the commander of Pacific Command, directed the Carl Vinson strike group "to sail north and report on station in the Western Pacific."
Reuters and other news outlets reported on April 11 that the movement would take more than a week. The Navy, for security reasons, says it does not report future operational locations of its ships.
But even Mattis initially misspoke about the strike group's itinerary, telling a news conference that the Vinson had pulled out of an exercise with Australia.
The Pentagon has since corrected the record, saying the ship's planned port visit to Fremantle, Australia, was canceled - not the exercise with Australia's navy. On April 15, the US Navy even published a photo showing the Vinson transiting the Sunda Strait.
From April 16-18, the website Go Navy reported that the Vinson was in the Indian Ocean.
A US military official, speaking on condition of anonymity, said the Vinson carried out the exercises after passing through the Sunda Strait and wrapped them up this week.