US election campaign adverts take on IS and national security

There are three weeks until the mid-term elections in the US, and political advertising is in full swing.

Although campaign adverts typically focus on domestic issues, this year foreign policy is playing a more prominent role.

Many candidates are attacking their opponents' positions on national security and facing the threat from Islamic State (IS) extremists.

The BBC's Anthony Zurcher reports.

Produced by Ashley Semler