THE PRIMER is an initiative of independent researchers. The facts and analyses presented herein represent the authors’ own appreciation of published material and primary sources that were accessible to them during the course of the research. They do not represent any position of the government of the Republic of the Philippines, unless stated otherwise, nor of the publisher. The purpose of this Primer is to make available in a single updated volume a simplified and objective rendering of the historical background, current conditions, pertinent issues and policy questions regarding the territorial and maritime disputes in the West Philippine Sea. It is intended to assist students, researchers, media practitioners, non-specialist members of the civil service, as well as the general public, in deepening their understanding of the many different issues of the West Philippine Sea disputes. The questions and answers are framed from a Filipino perspective that focuses on information that the authors considered to be most important and of interest to citizens of this country, rather than information that may be highlighted by various foreign authors, organizations or governments. The contents are not intended as advocacy of any particular position or policy recommendation. As proposed by some stakeholders, this updated version includes more recent developments pertaining to Ayungin Shoal, and the International Tribunal on the Law of the Sea (ITLOS) arbitration process initiated by the Philippines with respect to China's 9-dash line claim.