In this February 11, 2020, file photo, Syrian government helicopter is shot by a missile in Idlib province, Syria. Syria’s civil war has long provided a free-for-all battlefield for proxy fighters. AP
In this February 11, 2020, file photo, Syrian government helicopter is shot by a missile in Idlib province, Syria. Syria’s civil war has long provided a free-for-all battlefield for proxy fighters. AP

After rebels down regime helicopters, reminders of one of Syrian war's great controversies