Some are expressing surprise that Sudan is contributing aircraft and even ground troops to the Saudi-led coalition bombing the Houthis in Yemen. Sudan has relatively few good friends in the region, and in the past has been one of the rare Sunni Arab countries to maintain friendly relations with Iran. (Oman, which is partly Ibadi, also does, but is not actively participating in the coalition.)
Sudanese President Bashir is wanted by the International Criminal Court, though Egypt has welcomed him on visits in the past and this week he visited King Salman in Saudi Arabia. Gulf press reports have said that Sudan has deployed either two or three aircraft to the coalition, and there are also reports that it has offered ground troops.
Interpreting this as "Sudan changes sides," as some are doing, is probably an exaggeration of reality. As a Red Sea country whose main oil exports pass through the pipeline terminal at Port Sudan, Sudan, like Egypt and Saudi Arabia, obviously has concerns about the stability in Yemen. But its participation is a bit surprising: Egypt and Saudi Arabia are extremely close in the Sisi era, and all the GCC states except Qatar and Oman are also predictable (and Qatar is on board with the coalition. Pakistan has close military ties with the Saudis, and Jordan and Morocco are also frequent allies of their fellow conservative monarchies in the GCC.
But Sudan, despite its obvious concerns as a Red Sea littoral state, is not the most obvious volunteer. But the country's economy is a mess and Bashir is internationally ostracized. It may seem cynical to suggest that the sudden enthusiasm for Saudi Arabia is financially motivated, but Sudan is the least obvious member of the coalition.