Conversation so far:
When did P. W. Botha enter Parliament?
1948
What happened to P. W. Botha after entering Parliament?
In 1958 Botha was appointed Deputy Minister of Internal Affairs by Hendrik Verwoerd.
When did P. W. Botha win the the 1948 election?
1948
Who was P. W. Botha's opponent in the 1948 election?
JP Marais
What happened to P. W. Botha after the 1948 election?
In 1958 Botha was appointed Deputy Minister of Internal Affairs by Hendrik Verwoerd.
What was P. W. Botha's next position after being appointed as the Deputy Minister of Internal Affairs?
Minister of Coloured Affairs
What was P. W. Botha's next position after being Minister of Coloured Affairs?
P. W. Botha was appointed Minister for Defence by Verwoerd's successor B.J. Vorster, upon Verwoerd's murder, in 1966.
What was P. W. Botha's impact as Minister for Defence?
The South African Defence Force reached a zenith, at times consuming 20% of the national budget, compared to 1.3% in 1968, and was involved in the South African Border War.

Question: How long was he a Minister for Defence?
Self-contained rewrite: How long was P. W. Botha a Minister for Defence?