Bosphorus

The length of the strait is about 30 km. The maximum width of the strait is 3700 m (in the north), the minimum is 700 meters ^[2] . The fairway depth is from 33 to 80 m ^[3] .

The theory of the Black Sea flood assumes that the Bosphorus was formed about 7600 years ago. Before, the level of the Black and Marmara Seas was significantly lower, and they were not connected. At the end of the last ice age, as a result of the melting of large masses of ice and snow, the water level in both reservoirs rose sharply. A powerful stream of water in just a few days has made its way from one sea to another - the bottom topography and other signs testify to this.

Morphology

The strait has an erosive origin; represents an old river valley flooded with sea water in the Quaternary ^[4] . There are two currents in the Bosphorus - the desalinated upper one from the Black Sea to the Marmara Sea, to the south (speed 1.5–2 m / s) and the salty lower one — from the Sea of ​​Marmara to the Black Sea, as was established by Admiral Makarov in 1881-1882 (speed 0, 9-1 m / s) ^[5] . The salty course continues in the Black Sea with an underwater river .

According to one of the most common legends, the strait got its name thanks to the daughter of the most ancient Argiv king - the beautiful lover of Zeus named Io was turned into a white cow by him in order to avoid the wrath of his wife Hera . Unhappy Io chose the waterway to salvation, diving into the blue of the strait, which since then has been called "cow ford" or the Bosphorus ^{[6] [7]} .

The ancient Greeks also called the Strait "Bosporus of Thrace" to distinguish it from the "Cimmerian Bosporus" (the modern name is the Kerch Strait ).

The Bosphorus is one of the most important straits, as it provides access to the Mediterranean Sea and the oceans of a large part of Russia , Ukraine , the countries of Transcaucasia and southeastern Europe . In addition to agricultural and industrial products, oil from Russia and the Caspian region plays a large role in exports through the Bosphorus.

The Bosphorus Strait occupies a special place among the most known most impassable straits in the world due to the heavy traffic of transit vessels, ferry crossings, small vessels, currents of up to 6 knots and sudden changes in weather in the autumn-winter period. Many shipping companies recommend that captains use pilots for the transit passage of the Bosphorus Strait. The transit speed in the strait should be no more than 10 knots. For passage through the straits, a lighthouse fee of about one thousand dollars is levied, depending on the class of the vessel ^[8] .

The solution to the problem of the passage and congestion of the strait is supposed to be in the form of the construction of a shipping channel west of Istanbul from 50 to 100 km long ^[9] .

The shores of the strait are connected by three bridges and two tunnels (from north to south):

• Sultan Selim the Terrible automobile-railway bridge (1408 m; completed in 2016) in the northern part of the strait, on the Black Sea coast;
• Sultan Mehmed Fatih automobile bridge (1090 m; built in 1988) 5 km north of the first bridge;
• automobile Bosphorus bridge with a main span of 1074 meters (completed in 1973);
• Marmaray railway tunnel between two districts of Istanbul - Kazlycheshme on the European coast and Ayrylykcheshme - on the Asian (total length - 13.6 km, under water - 1.4 km; opened in 2013) ^[10] , which combined high-speed transport systems of the European and Asian parts of Istanbul ;
• The automobile tunnel between the Kazlycheshme and Geztepe districts (length - 14.5 km, of which 5.4 km under the strait at a depth of 106 meters), opened in December 2016 ^[11] .

As part of the only passage between the Black Sea and the Mediterranean Sea, the Bosphorus is of great importance in trade and military affairs. Control over it was the goal of a number of conflicts, in particular the Russo-Turkish War (1877-1878), as well as the attacks of the Allied powers on the Dardanelles during the battle of 1915 at Gallipoli during the First World War.

Ancient Greek, Persian, Roman and Byzantine eras (before 1453)

Greek city-state of Athens in the 5th century BC e., depending on the import of grain from Scythia , maintained allied relations with cities that controlled the straits, such as Byzantium .

Persian king Darius I the Great , trying to subdue the Scythians , crossed the Bosphorus, and then moved to the Danube River. His army crossed the strait along a floating bridge built from boats. Many years later, during the invasion of Xerxes I in Greece, a similar boat bridge was built across the Dardanelles (Hellespont) .

Ottoman era (1453-1922)

On May 29, 1453, the Ottoman Empire conquered Constantinople after a long siege, during which the Ottomans built fortifications on both sides of the strait, Anadoluhisara (1393) and Rumelihisara (1451), preparing not only for the main battle, but also for establishing long-term control over the Bosphorus and the passing through it by water. Together with Christopher Columbus' first trip to America in 1492, the conquest of Constantinople in 1453 is considered one of the events that put an end to the Middle Ages and marked the transition to the Renaissance and the era of discoveries .

During its heyday between the sixteenth and eighteenth centuries, the Ottoman Empire used the strategic importance of the Bosphorus to expand its regional ambitions and establish control over the entire Black Sea, which they considered the "Ottoman lake" ^[12] .

Subsequently, several international treaties regulated the passage of ships in these waters. According to the agreement of Gunkar Iskelesi of July 8, 1833, the Bosporus and Dardanelles straits were to be closed at the request of Russia for ships of other powers. Under the terms of the London Convention on the Straits , concluded July 13, 1841 between Russia , the United Kingdom , France , Austria and Prussia , the "ancient rule" of the Ottoman Empire was restored by closing the Turkish Straits for any warships, with the exception of the ships of the Sultan's allies during the war ^{[ 13]} .

After World War I, the Treaty of Sèvres of 1920 demilitarized the strait and made it an international territory under the control of the League of Nations .

Turkish Republican Era (1923 — present)

In accordance with the Lausanne Treaty (1923), the straits were returned to Turkey, but all foreign warships and commercial vessels were allowed free passage. Subsequently, the navigation regime was regulated by the Montreux Convention on the regime of straits of July 20, 1936. According to it, Turkey reserves the right to limit shipping of non-Black Sea countries. Turkey remained neutral during World War II until February 1945, and at that time the straits were closed to warships of the warring countries, although some German auxiliary vessels were allowed to transit. This, as well as Stalin's demands for the return of the Turkish provinces of Kars, Artvin and Ardahan to the Soviet Union (lost by Turkey in the Russian-Turkish war of 1877-1878, and returned by the Kars Treaty in 1921) were considerations in Turkey's decision to abandon neutrality in foreign affairs. Turkey declared war on Germany in February 1945, but did not participate in offensive operations. ^[14]

At the beginning of the 21st century, the Turkish straits became especially important for the oil industry. Tankers export Russian oil primarily to Western Europe and the United States through the Bosphorus and Dardanelles. In 2011, Turkey planned a 50-kilometer canal through Silivri as a second waterway ^{[15] [16]} .

• Golden Horn
• Strait of Kerch (in ancient Greece was called the Cimmerian Bosporus)
• Bosphorus East
• Trans-balkan pipeline

• Ulyanitsky V.A. Dardanelles, the Bosphorus and the Black Sea in the XVIII century . - M .: Type. A. Gatzuli, 1883 .-- 721 p.

• Bosphorus // Military Encyclopedia : [in 18 vol.] / Ed. V.F. Novitsky [et al.]. - SPb. ; [ M. ]: Type. t-va I. D. Sytin , 1911-1915.
• Bosphorus // Brockhaus and Efron Encyclopedic Dictionary : in 86 volumes (82 volumes and 4 additional). - SPb. , 1890-1907.