Michael Haley, a major in the South Carolina Army National Guard, is deployed in Africa and previously served in Afghanistan.
Trump attacked his only remaining rival for the Republican presidential nomination at a huge rally in her home state of South Carolina on Saturday.
'Where's her husband? Oh, he's away… What happened to her husband? Where is he? He's gone,' he said in Conway.
DailyMail.com revealed new details last month of claims by two men that Haley had extramarital affairs with them in 2008. Haley denied both of them.
Trump appeared to refer to the alleged affairs as he continued 'he knew, he knew'.