International collaboration for disaster response is an increasing phenomenon. Japan-United States joint field exercises have been conducted annually since 2004, triggered by an incident in which a US helicopter crashed into a university campus in Okinawa, Japan. The fifth Japan-US disaster field exercise was conducted testing the disaster response of the Okinawa government and US military.

The simulated exercise involved a US Navy aircraft that crashed into a city center in Okinawa, Japan. There were 16 simulated casualties that included US military members and Japanese citizens. The participants in this exercise were US military members, including the Disaster Assistance Response Team (DART) and local rescue and medical teams including the Okinawa Disaster Medical Assistance Team (DMAT). Data were gathered from the joint debriefing session held by both medical teams. Furthermore, interviews with team leaders from both nations were conducted and feedback obtained.

Lack of communication and inaccurate communication remained the root of most problems encountered. There were several miscommunications at the scene due to the language barrier and ignorance of different medical teams' capability and method of practice. Due to the unclear signage of the initial triage zone, another triage zone was developed later by a second medical team. Confusion regarding gathering information and order of transport also was witnessed. The capabilities of team members were not well known between teams, resulting in inappropriate expectations and difficulty in effective cooperation.

Understanding the systems and backgrounds of each medical team is essential. Signs or symbols of key elements including triage areas should be clear, universal, and multilingual. Communication remains the Achilles' heel of multi-national disaster response activities.