Turkish-backed rebels have uncovered a large network of tunnels built by Kurdish fighters before they were forced to retreat from northern Syria last week.

The complex network was discovered abandoned in the border city of Tal Abyad and is believed to have been built by the US-aligned Syrian Democratic Forces anticipating a Turkish invasion, Reuters reported.

The underground network, which includes operations rooms, lounges and food storage chambers, was built as a contingency after Turkey bloodily seized the Kurdish city of Afrin in north-western Syria in 2018, Foreign Policy reported.

But the tunnels were abandoned after the Kurds agreed to withdraw from an Arab-majority stretch of border following President Trump’s announcement he was pulling American support and Turkish forces quickly moved in.

Photos taken Sunday shows Turkish-backed fighters inspecting the tunnels and burning a Kurdish flag.

Their hopes of destroying the tunnels, however, have been foiled by the fact much of the network runs under civilians’ homes, according to the Reuters report.

Trump’s decision to bring back troops from Syria, which he has repeatedly defended, has been criticized by Democrats and a handful of Republicans who say the US is abandoning its Kurdish allies who helped defeat the Islamic State.