The world's straits make up only a tiny portion of the oceans, but they have an importance out of all proportion to their size. The ease with which they can be blockaded has made them a focal point of nations seeking to protect the trade on which, in a globalized world, they increasingly depend. Yet their control by one country, even if defensive in intent, has always appeared a threatening to its rivals.
It is no surprise that the straits' importance made them central features of the two world wars. In WWI, Russia was cut off from its normal trade routes by Germany's control of the Danish Sound and by Turkey's control of the Turkish Straits. In turn, Germany was economically isolated by Britain's control of the Dover Straits and the sea passage between Norway and Scotland. In World War II, Germany planned to capture the Suez Canal to cut Britain's trade with India, and Japan.
In 1967 and 1973, Egypt closed the Suez Canal in an attempt to put force the Western countries to stop supporting Israel. More recently, China has voiced concern about the threat that foreign (read American) control of the Straits of Malacca poses to its vital foreign trade.
Now Al-Qaeda shows that it too understands the importance of the world's straits (and also of modern PR methods) in the first edition of its new glossy magazine.