BACKGROUND Emergency department (ED) overcrowding may affect the ability to provide quality care and maximize patient flow. Study objectives To analyse the impact of the control of the patient flow during a conflict on ED overcrowding. METHODS During a recent military conflict in Israel the Ministry of Health issued a directive aimed at redirecting the patient flow to EDs in a metropolitan area. The admissions were monitored to identify trends and determine if any changes occurred after the policy change. RESULTS Medical admissions in the only level I trauma centre decreased by 6.5% after the notification, while rising in two other level II hospitals by 3.7% and 4.3%, respectively. Pre- and post-conflict trauma admissions in the level I trauma centre dropped by 2.2% and increased by 6.4% and 1.8%, respectively, in the other hospitals. CONCLUSIONS It is possible to direct the flow of patients to EDs and rationalize the use of resources, making it possible for patients to be admitted to EDs best able to care for them. These findings are especially relevant to emergency situations, but also to non-emergent situations in which control of patient flow may be required. Direct communication with the public is recommended to minimize the implementation time of directives regarding patient flow.