He became the 11th NATO Secretary General on 5 January 2004, succeeding Lord Robertson, who held the post from 1999 until 2003. The announcement was made on 22 September 2003. As Secretary General, De Hoop Scheffer urged NATO members to contribute more to NATO operations such as the International Security Assistance Force in Afghanistan. He "informed a NATO conference that 'NATO troops have to guard pipelines that transport oil and gas that is directed for the West,' and more generally to protect sea routes used by tankers and other 'crucial infrastructure' of the energy system".