Defence minister Tobias Ellwood says he is "very sad" to see Penny Mordaunt leave the role of defence secretary and has backed her successor Ben Wallace to do a good job.
Speaking about the new appointment, Tobias Ellwood, Minister for Defence People and Veterans, said: "I know that Ben Wallace will do an incredible job.
"He's a good friend, with Army experience.
"He is very thorough, he comes from just doing the security brief as well, so very understanding about what is happening across the world.
"I know that he will be passionate about securing more funding for the armed forces."
Ms Mordaunt was the first-ever female defence secretary but spent just 85 days in the cabinet.
Mr Ellwood said: "I don't understand what happened with Penny, I pay tribute to her hard work.
"It's a game of snakes and ladders."
The defence secretary change was one of a number of new appointments made by Prime Minister Boris Johnson, and comes at a time of tension with Iran.
"I wouldn't call it a crisis with Iran, there's been a spike in threat levels," Mr Ellwood said.
"We need to de-escalate tensions there, we are sending further assets to the region itself.
"But ultimately our decision making is not thwarted by this and I'm sure one of the first things the foreign secretary will be doing is making sure that he gets on top of what's happening there."
Before going into politics, Mr Ellwood spent six years in the Army with The Royal Green Jackets, serving in Northern Ireland, Cyprus, Germany, Gibraltar and Bosnia.
He was first elected as a Member of Parliament in May 2005 and began working as a defence minister in June 2017.
After Ben Wallace's appointment to the Ministry of Defence, there has been no news on whether other ministerial positions in the department will change.
"It's been a true honour to be the veterans minister," Mr Ellwood said.
"It's been a real pleasure to work with some incredible people and to further cause to support our brave veterans."