During his military career of 36 years in the Netherlands Armed Forces, Willem Tanis had the opportunity to organise and participate in several military national and international ceremonies. In the last eight years he held position in the personal staff of the Commander-in-Chief of the Royal Netherlands Army and the Chief of Defence Staff at the Netherlands Ministry of Defence. In these positions he took part in many official events and ceremonies.
After his retirement in 2006 Willem Tanis was asked by the Netherlands Minister of Defence to prepare the NATO Defence Ministerial Summit in 2007 and the AFSOUTH Defence Ministerial meeting in 2009. As Protocol Official he had to welcome and escort the NATO Defence Ministers.
From October 2011 till November 2012 Willem Tanis was the Chief of Protocol at the Floriade in Venlo. This horticultural world exhibition is held every 10 years in The Netherlands. During this time he prepared and executed more than 80 VIP visits by members of the Netherlands and foreign Royal Houses, Head of States, Ministers of Agriculture and Ambassadors.