In this study, naval historians from Australia, Canada, the United Kingdom, and the United States explore how their navies created an effective multinational, or "combined," framework of interoperability while under national rules of engagement. The authors address cases including maritime operations during the First Gulf War (1990-1991) and later (2001-2003) as part of Operation Enduring Freedom; off the Federal Republic of Yugoslavia in Operation Sharp Guard (1991-1996); and in East Timor during Operation Stabilise (1999-2000). This multinational naval force's success in each crisis depended not just on shared doctrine, training, tactics, and technology, but on the trust its sailors built in combined operations over time.