goodman. confirmation hearings for president-elect donald trump's key cabinet members begin monday. one of the first to go before congress will be trump's pick for homeland security secretary, retired marine general john kellylly was formerly the head of united states southern command, where he oversaw the military prison at guantanamo. he is repeatedly testified to congress that the u.s.-mexico border represents a threat to national security, leading many to worry he will escalate the militarization of the border and u.s. immigration policy overall. he's one of three generals trump has nominated for cabinet and cabinet-level positions. that includes retired general james "mad dog" mattis as defense secretary. he is likely to face questions about his actions in may 2004, when he ordered an attack on a small iraqi village that ended up killing more than 42 people attending a wedding ceremony. mattis went on to lead united states central command from 2010 to 2013, but the obama administration cut short his tour over concerns mattis was too hawkish on iran, reportedly calling for a series of covert actions there. he only retired from the military in 2013, meaning h he wiwill need congress to waive rules requir