Maven – how to delete contents of a folder during a clean phase?

Add this includes section to your fileset definition

<build>
    <plugins>
        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-clean-plugin</artifactId>
            <version>2.4.1</version>
            <configuration>
                <filesets>
                    <fileset>
                        <directory>war</directory>
                        <includes>
                            <include>**/*</include>
                        </includes>
                        <followSymlinks>false</followSymlinks>
                    </fileset>
                </filesets>
            </configuration>
        </plugin>
    </plugins>
</build>