Following the 2015 general election and the formation of the majority Cameron government, he became Parliamentary Under-Secretary of State in the Northern Ireland Office.

In 2016, he was appointed Minister of State for Security and Economic Crime by Theresa May, holding the position until she left office in July 2019.

[5] In July 2023, Wallace announced that he intended to resign as Secretary of State for Defence at the next Cabinet reshuffle, and that he would not be seeking re-election as an MP at the 2024 general election.

[2] In April 1993, he was promoted lieutenant,[14] and later that year was mentioned in dispatches[15] for an incident in Belfast where the patrol he was commanding captured an entire IRA active service unit (ASU) attempting to carry out a bomb attack against British troops.

[18] Wallace was on duty on the night of the death of Diana, Princess of Wales, and was a member of the party sent to Paris to bring home her body.

[20] He later explained that he had decided against seeking to become a regular officer and to continue after the age of thirty, as the part of the work he had really enjoyed was commanding soldiers, and this was likely to diminish after that point.

[21] Wallace entered politics after leaving the army, citing as a reason for this decision the experience he had commanding men from some of the UK's most economically deprived areas, which he averred could be improved by promoting a more aspirational society.

[23] His constituency was abolished for the 2010 UK general election, and Wallace was instead returned for the new seat of Wyre and Preston North with 26,877 votes and a majority of 15,844 (30.9%).

[19] On 4 September 2012, Wallace turned down a position as a Lord Commissioner of the Treasury during the cabinet reshuffle[citation needed] to remain Clarke's PPS.

[33] On 24 July 2019, Boris Johnson became prime minister and immediately appointed Wallace as Secretary of State for Defence, replacing Penny Mordaunt,[34] who was left out of the new government.

[35] In August 2019, Wallace was overheard discussing Johnson's controversial prorogation of parliament with Florence Parly, the French Armed Forces minister.

[49] In December 2021, Wallace met with Saudi Arabia's Crown Prince Mohammed bin Salman to discuss cooperation in various fields, especially defence, having discussed similar matters the previous year with Saudi Arabia's vice defence minister Prince Khalid bin Salman.

[50][51] In 2022, at an event to mark the 40th anniversary of the end of the Falklands War, Wallace declared Britain's determination to "stand up to bullies".

[6] The following day, Wallace said that a Russian invasion of Ukraine was "highly likely", and British citizens were being told by the Foreign Office to evacuate while commercial means were still available.

[55] Ukraine's ambassador to the UK, Vadym Prystaiko, said Wallace's comparison of diplomatic efforts with Russia to the appeasement policies of the 1930s was unhelpful,[56] saying now is the wrong time to "offend our partners".

[58] On 21 March 2022, clipped footage of Wallace in a prank call by Russian pranksters Vovan and Lexus was released online.

[62] Wallace was perceived as responsible for initial British reluctance to send Challenger 2 tanks to Ukraine in March 2022, saying that the idea "wouldn't work".

[63][64] Boris Johnson and his German counterpart Olaf Scholz agreed on 8 April that both European allies would withhold their Western-designed main battle tanks from the fray.

Johnson instead chose to backfill the Polish Army, thus allowing them to send their obsolete T-72s to Ukraine,[63] while they waited for their order of South Korean K2 Black Panther replacements.

[73] On 19 January 2023 Wallace together with the defence ministers of Estonia, Poland, Latvia and Lithuania; and the representatives of Denmark, the Czech Republic, the Netherlands, and Slovakia issued the Tallinn Pledge, "to reaffirm our continued determination and resolve to supporting Ukraine in their heroic resistance against the illegal and unprovoked Russian aggression.

"[74][75][76][77][78] On 21 June 2023, Wallace ruled himself out of the running to become the next NATO Secretary-General after rumours spread that the US were in favour of Jens Stoltenberg staying in post.

[80][81][82] On 15 July 2023, Wallace announced his intention to resign as Secretary of State for Defence at the next Cabinet reshuffle and confirmed that he would not be seeking re-election as an MP at the 2024 general election.

Wallace was also the longest-serving participant in the current UK Cabinet by continuous service; attending without interruption since his 2016 appointment as Minister of State for Security.

In April 2024 after the 300-unit drone strike by Iran on Israel Wallace said the event "had dashed his own hopes that reformers would one day triumph over the hardliners.

"[84] He wrote an op-ed in the Daily Telegraph and advised the West to "hit back twice as hard" against Iran and Russia and "not stop until they get the message".

[85][86] In February 2024 Wallace expressed his displeasure over German Chancellor Olaf Scholz' refusal to give Ukraine the Taurus missile.

He echoed past UKCGS Sir Patrick Sanders' exit remarks about Western nervousness over Russian nuclear sabre-rattling rhetoric.

[89] In September Wallace, speaking to BBC Radio 4's Today programme, said that the "tug of war" over long-range missiles that can strike targets in Russia, such as Storm Shadow, was repetitive nonsense and only helped Putin.