Such reviews can happen when political or economic factors dictate, such as upon a change of Government.
The Defence Review will normally result in the publication of a policy document, styled a White Paper and released to parliament as a Command paper, setting out the broad aims, objectives, and rationale for the policy and strategy.
The United Kingdom governmental carries out Defence Reviews infrequently, usually upon a change of government or major political event, such as just after the Collapse of Communism.
British Defence Reviews since the end of World War II include: United Kingdom governments have also conducted policy reviews which cover specific aspects of defence but do not purport to be fundamental reappraisals of overall defence policy and strategy.
Examples of these include: The main difference between the United Kingdom Ministry of Defence and the United States Department of Defense as pertains to the review cycle is frequency.