Venezuelan national guardsmen at the Tienditas International Bridge, which links Colombia and Venezuela, near Urena, Venezuela, February 8, 2019. Associated Press

Juan Guaido, the Venezuelan opposition leader who has been recognized as interim president by dozens of countries, said Friday that 600 military personnel had defected in the week since Venezuelan President Nicolas Maduro ordered them to block the entry of aid sent by the US as part of an effort to oust him.

Since 2014, some 4,300 members of the country's national guard - all non-commissioned officers or enlisted personnel, representing about 6% of the force - have deserted, according to a document signed by the guard's commander in December.

The military has been described as Venezuela's "king-maker" - a force that has kept Maduro in power amid deadly protests and international opprobrium.

Read more: Venezuela's 'king-maker' is fraying, and nobody knows what comes next

But that support is not total.

Many senior military leaders have personal and financial interests at stake - protecting special privileges, like higher pay, and avoiding prosecution for involvement in illegal activity, like drug smuggling. Junior officers and rank-and-file troops, however, have no such interests.

"Many, many low-level former police and military figures are among the over 3 million Venezuelans who have fled the country" over the past several years, Geoff Ramsey, assistant director for Venezuela at the Washington Office on Latin America, told Business Insider. "What is new about this latest wave is the rate of defections."

In recent days, some of the troops who have turned on Maduro have explained why.