Johnny Mercer, the UK's first cabinet Minister for Veterans' Affairs, has been sacked from the role in new Prime Minister Liz Truss' first cabinet reshuffle.
In a statement posted on social media, he said was "disappointed" to have been "relieved of my duties in Government" by Ms Truss.
"I am disappointed to leave a role I established, leading a team that I established. But any prime minister is entitled to reward her supporters, and I accept her decision," the Plymouth Moor View MP said.
The Conservative MP was named the Minister for Veterans' Affairs in July and after the announcement said "promises to our veterans are important, and will be kept".
In his letter, he says he has to accept that he "will never have the qualities required for enduring success in politics" and is considering his future.
Mr Mercer, a former soldier with a long connection to the Armed Forces, has campaigned tirelessly for veterans and in particular to stop former soldiers from facing court proceedings over military actions and campaigns from decades ago.
In March, Mr Mercer also revealed he secretly travelled to Ukraine's capital Kyiv where he visited injured people in hospital, saying on his Twitter he witnessed "total carnage" alongside demonstrations of "incredible human spirit".
Coming from a military family, Mr Mercer graduated from the Royal Military Academy, Sandhurst, in 2002.
He served in a number of roles across the globe, including completing three tours of Afghanistan, before retiring from the Army in December 2013 with the rank of captain.