Bosphorus’s amateur ship spotters keep watch on global power struggle

They're up before dawn to track traffic on the busy strait - and their sightings of warships can help to predict Russian strategy. The Observer meets 'a nerdy little community'

The Bosphorus, the magnificent strait dividing Istanbul in two, is named after Io, a mortal lover of the god Zeus, who was cursed by his wife Hera to wander the earth in the form of a white heifer: the name comes from the Greek bois, cow, and poros, passage.

Io may have been the first to cross the waterway dividing Europe from Asia, but she was certainly not the last. As the route from the Black Sea to the Mediterranean, the Bosphorus offers enormous geopolitical power to whoever controls it. The city of Constantinople was founded on either side of its shores, successively the seat of the Roman, Byzantine and Ottoman empires. Today, the Bosphorus breathes calmly and quietly beneath the hills of modern Istanbul, but its waters are still full of international intrigue.