As part of the UK's move towards robots, drones, and cyber warfare, the country is expected to reduce its army by about 10,000 soldiers.
Numbers in the UK's regular army will be reduced to about 70,000 soldiers, reports the BBC.
The defence review is likely to see the loss of some tanks and aircraft - but the government said there would be "more ships, submarines and sailors".
UK Defence Secretary Ben Wallace will make a statement in the Commons later. Wallace told BBC One's Andrew Marr Show on Sunday that he was making decisions in the context of an increased defence budget.
There were 80,010 soldiers in the UK's regular army in January 2021, latest figures showed, down from 86,080 in October 2015.
The latest reduction in the number of soldiers could be made through "natural" movement, with those who leave the service not replaced by new recruits.
As part of the military restructure, the Royal Marines will be transformed into a new Future Commando Force, taking on many of the traditional tasks of the special forces - the SAS and SBS.
The force will receive more than £200 million of direct investment over the next decade to carry out maritime security operations and to "pre-empt and deter sub-threshold activity, and counter state threats".
Following the publication last week of the separate so-called integrated review of foreign and defence policy, ministers have said big changes are necessary to create a more agile military.
As part of that review, the government increased the cap on UK nuclear warheads from 180 to 260.