<p>The Union Defence Force (UDF) experienced constant changes in its size and organisation during the first few decades of existence since being established on 1 July 1912. During the First World War it's size increased, 2 only to decrease again with demobilisation after the War. Another upward trend was experienced over the period 1922-1926, with the first line of defence increasing in number during 1924 from 10 000 to 25 000.3 The Depression of 1929-1933 stopped this tendency' resulting in the disbandment of no less than 49 Active Citizen Force (ACF) units.</p> <p>During 1933 however, it became clear that the Depression was drawing to an end and economic revival within South Africa became a reality. At the same time, that is during 1933, the top management within the Ministry of Defence as well as the UDF were replaced. Advocate Oswald Pirow was appointed as Minister of Defence and Maj. Gen. A.J.E. Brink as Secretary of Defence. Sir Pierre van Reyneveld was appointed as Chief of the General Staff (CGS).5 The expectation of economic prosperity urged the new top management, to consider the reorganisation and expansion of the UDF. These expectations led to an announcement to Cabinet by Oswald Pirow on 16 October 1933 of his intend to re-evaluate the Union's security situation and to implement the expected reorganisation resulting from the re-evaluation by means of a five-year plan.6 The five-year plan was announced in Parliament on 2 May 1934 and with time, became known as "Oswald Pirow's Five-year Plan". On studying the sources however it is clear that Pierre van Reyneveld and not Oswald Pirow was the true driving force behind the plan. Pierre van Reyneveld as CGS however was responsible for most of the planning and for drawing up the plan. As Minister of Defence Oswald Pirow was the public figure with whom the plan was associated, hence the name: "Oswald Pirow's Five-year Plan".</p>