Deploying external wars in Tomcat via IntelliJ Idea

Since the link on the accepted answer is dead, here is the process, step by step (I'm using Intellij 14):

1) Select Run/Edit Configuration

2) If no Tomcat Run Config exists yet, create one

3) Select the Tomcat run config just created, on Deployment tab, under Deploy at server startup section, click the "+" (right sidebar), select External source, and select your war file.