He served for four years as a commissioned officer in the Japan Ground Self-Defense Force (20th Infantry Regiment and Airborne Training Unit).

Meanwhile Teru Fukui, who had held the 1st district since 1996, switched to the Shikoku proportional representation block.

Nakatani supported Koichi Kato and Taku Yamasaki's no-confidence motion against Prime Minister Yoshiro Mori in 2000, and was appointed to head the Japan Defense Agency under Prime Minister Junichiro Koizumi in the following year.

On 28 April 2015, Nakatani was among the guests invited to the state dinner hosted by U.S. President Barack Obama in Abe’s honor at the White House.

[4] In a joint letter initiated by Norbert Röttgen and Anthony Gonzalez ahead of the 47th G7 summit in 2021, Nakatani joined some 70 legislators from Europe and the US in calling upon their leaders to take a tough stance on China and to "avoid becoming dependent" on the country for technology including artificial intelligence and 5G.