Saudi Arabia’s King Salman has ordered the country’s National Guard — considered the Kingdom’s best trained and equipped military force — to join the military campaign against Iranian-backed Shiite rebels in neighboring Yemen.

National Guard troops had already deployed along Saudi Arabia’s southern border with Yemen, but the order from Salman on Tuesday could pave the way for a long-discussed ground incursion into Yemen to confront the rebels, known as Houthis.

The Saudi-led coalition pounded Shiite rebels in Yemen on Tuesday, killing 20 in a city in the country’s west as the civilian death toll rose to 38 from airstrikes the day before in the capital, Sanaa, officials said. […]