In this position he has overall responsibility for the business of the Ministry of Defence.
This involves overseeing operational strategy, defence planning and resource allocation.
In his first keynote speech as Defence Secretary, Mr Williamson said "frankly, Russia should go away and should shut up" in response to the Salisbury nerve agent attack in March.
In the last few months, Mr Williamson has visited the 2nd Battalion Royal Gurkha Rifles in Brunei, met with British personnel from the NATO battle group stationed in Estonia and travelled to RAF Akrotiri to meet personnel fighting Islamic State.
Mr Ellwood served on the Armed Forces Bill Committee as a member from January 2011 to March 2011.
Previously he held the position of Parliamentary Under-Secretary of State for Foreign and Commonwealth Affairs between July 2014 and June 2017.
In terms of voting Mr Ellwood supported the use of UK military forces in overseas combat operations.
Between 2010 and 2015 he voted in support of airstrikes in Iraq and Syria against ISIL, for the establishment of a no-fly zone in Libya and for the continued deployment of UK armed forces in Afghanistan.
Between 2006 and 2007 Mr Ellwood voted in support of inquiries into the Iraq war, but then in 2016 voted against an investigation into the contrast between public statements and private actions in the run up to the war.
In 2011 he voted against a legally binding Military Covenant set out in law and against considerations having to be made when considering a person’s military service when setting policy concerning healthcare education and housing policy.
Mr Ellwood spent six years in the British Army. He served with the Royal Green Jackets in Northern Ireland, Cyprus, Kuwait, Germany, Gibraltar and Bosnia and remains an active Army Reservist today.
Tobias Ellwood was elected as the Conservative MP for Bournemouth East in May 2005, then subsequently re-elected in 2010, 2015 and 2017.
Mr Andrew will be responsible for the Equipment Plan, defence industry and exports.
This will cover nuclear enterprise, innovation and information computer technology.
According to the records website, They Work For You, Mr Andrew consistently voted for the use of British military forces in overseas combat operations and consistently for military action against Islamic State.
The same records show the new Defence Minister also consistently voted for replacing Trident with a new weapons system but voted against investigations into the Iraq War.
Earl Howe - Minister of State for Defence
Lord Howe was appointed Minister of State for Defence in May of 2015 and also holds the position of Deputy Leader of the House of Lords.
In this unpaid role, the Minister is responsible for ceremonial duties, commemorations and acts as spokesman for all defence matters in the House of Lords.
These topics range from engagements with retired senior defence personnel to arms control and proliferation.
Last year, Lord Howe received a visit from Brunei’s Deputy Minister of Defence.
The Deputy Minister of Defence First Admiral (Rtd) Dato Seri Pahlawan Haji Abdul Aziz attended the @UKSEC_Expo last week in London, calling on The Rt Hon. Earl Howe, Deputy Leader of the House of Lords & Minister of State for Defence, United Kingdom: https://t.co/hTBOB09UXspic.twitter.com/JfPmVRsecs