Why Estonia is on the front line of Putin's war with Europe

It's the small Baltic state that's no stranger to being invaded - having been occupied by both Nazi Germany and the Soviet Union.But while many hope it will never happen again, there are fears in NATO and beyond that Estonia is next on Vladimir Putin's hitlist.So how is the country preparing for the threat from Russia? And could Estonia really be on the front line of a future war in Europe?Niall is joined by the outgoing UK ambassador to Estonia, Ross Allen.