By Jonathan Head
BBC News, Istanbul
The first train service in decades has set off from northern Iraq to Turkey.
Both countries hope the re-opening of the historic rail link will contribute to the fast-growing trade between them.
Germany began building the Berlin to Baghdad railway a century ago, hoping to open a route through Turkey to the Gulf. It took three decades to finish.
But the two recent conflicts in Iraq have taken a toll on the rail network. There has been no regular service to neighbouring countries since the 1980s.
But that should change now, with the first train leaving the city of Mosul on Tuesday and due to arrive in the eastern Turkish city of Gazientep 18 hours later, before making the return journey.
For a distance of just 500km (311 miles), that is pretty slow going; running through Syria, the train has to cross two international borders.
But the revived rail link symbolises the increasingly close ties between the three countries.
Having overcome its fear of Kurdish nationalism, Turkey now does about $10bn of trade with Iraq's Kurdish regional government every year - about 80% of goods sold there are Turkish.
Relations between Iraq and Syria are more fragile - in the past Syria has been accused of backing the insurgents behind several big bomb attacks in Iraq.
But trade between them - and between Syria and Turkey - is growing rapidly.
Turkey is gradually upgrading its railway network with high-speed routes and Iraq also plans big investments in its railways.
The Turkish government is now talking of a fast rail link running all the way to Pakistan.