The mission has been running for more than four years, beginning in September 2014 over Iraq when the Royal Air Force flew its first combat sorties of the operation.
Air strikes over Syria were first launched December 2015, following approval from the British Government.
The UK is the second largest contributor behind the US, with jets flying missions from RAF Akrotiri in Cyprus.
Since Op Shader began, the RAF has conducted more than a thousand air strikes over Iraq and Syria, using more than 4,300 weapons launched from Tornado, Typhoon and Reaper aircraft.
The RAF carried out its 1,000th air strike against IS, also known as Daesh, in September 2017.
History of Operation Shader
The British operation against so-called Islamic State began in Iraq on 26 September 2014 following a formal request for assistance by the Iraqi government.
In October 2014, the UK operation extended also to Syria, where the Royal Air Force conducted several surveillance flights. MQ-9 Reaper drones based in Cyprus were responsible for 30% of aerial surveillance over Syria.
Tornado jets have been involved since the beginning of the mission. Typhoon aircraft joined the operation in late 2015, when Parliament voted to extend the air campaign against Daesh to Syria.
Currently, tri-service personnel are manning roles with the Global Coalition's headquarters throughout the Middle-East, including in Baghdad where there are UK advisors working alongside Iraqi military personnel in the Iraqi Operational Command.
On Monday, the Defence Secretary confirmed that IS has not been completely defeated, and that there is an "ongoing threat" from the militants, but that all areas once occupied by Daesh in Iraq and Syria have been liberated.
How many Armed Forces personnel have been deployed?
Personnel from across the tri-services are involved in Op Shader.
Royal Air Force
The majority of UK personnel have come from the RAF.
In 2014/15 a total of 1,950 RAF personnel were deployed, with the number growing each year. By 2017/18, 2,230 RAF personnel were involved in Op Shader.