Choke point in the context of "String of Pearls (Indian Ocean)"

Gibraltar (/dʒɪˈbrɔːltər/ jih-BRAWL-tər, Spanish: [xiβɾalˈtaɾ]) is a British Overseas Territory and city located at the southern tip of the Iberian Peninsula, on the Bay of Gibraltar, near the exit of the Mediterranean Sea into the Atlantic Ocean (Strait of Gibraltar). It has an area of 6.8 km (2.6 sq mi) and is bordered to the north by Spain (Campo de Gibraltar). The landscape is dominated by the Rock of Gibraltar, at the foot of which is a densely populated town area. Gibraltar is home to around 34,000 people, primarily Gibraltarians.

Gibraltar was founded as a permanent watchtower by the Almohads in 1160. It switched control between the Nasrids, Castilians and Marinids in the Late Middle Ages, acquiring larger strategic clout upon the destruction of nearby Algeciras c. 1375. It became again part of the Crown of Castile in 1462. In 1704, Anglo-Dutch forces captured Gibraltar from Spain during the War of the Spanish Succession, and it was ceded to Great Britain in perpetuity under the Treaty of Utrecht in 1713. It became an important base for the Royal Navy, particularly during the Napoleonic Wars and World War II, as it controlled the narrow entrance and exit to the Mediterranean Sea, the Strait of Gibraltar, with half the world's seaborne trade passing through it.

The Strait of Hormuz (/hɔːrˈmuːz/ Persian: تنگهٔ هُرمُز Tangeh-ye Hormoz listen, Arabic: مَضيق هُرمُز Maḍīq Hurmuz) is a strait between the Persian Gulf and the Gulf of Oman. It provides the only sea passage from the Persian Gulf to the open ocean and is one of the world's most strategically important choke points. It has been so for centuries, with vast hinterlands rich in luxury trade good, but no easy access to lucrative trading ports. Babur's memoirs recount how almonds had to be carried from the distant Ferghana region in Central Asia to Hormuz to reach markets.

On the north coast lies Iran, and on the south coast lies the Musandam Peninsula, shared by the United Arab Emirates and the Musandam Governorate, an exclave of Oman. The strait is about 104 miles (90 nmi; 167 km) long, with a width varying from about 60 mi (52 nmi; 97 km) to 24 mi (21 nmi; 39 km).

The Shanhai Pass (simplified Chinese: 山海关; traditional Chinese: 山海關; pinyin: Shānhǎi Guān; lit. 'Mountain Sea Pass') is a major fortified gateway at the eastern end of the Great Wall of China and one of its most crucial fortifications, as the pass commands the narrowest choke point in the strategic Liaoxi Corridor, an elongated coastal plain between the Yan Mountains foothills and the Bohai Sea, which is the only easily traversable landway between North and Northeast China. It is located in present-day Shanhaiguan District, Qinhuangdao, Hebei province, on the east bank of the Shi River, with defensive walls stretching from the Yan Mountains all the way to the shores of the Liaodong Bay.

Throughout Chinese history, garrisons around the pass served as frontline defensive outposts against raids and incursions into the North China Plain by various non-Sinitic ethnic groups from the Northeast (also known as Manchuria since the 19th century), including the Dongyi, Donghu (Xianbei and Wuhuan), Khitan and Jurchen (Manchus). The current Shanhai Pass was built during the early Ming dynasty as the easternmost fortification of the Ming Great Wall, and was extensively reinforced after Yongle Emperor moved the capital from Nanjing to Beijing following the Jingnan campaign, making it the most important defensive barrier in all of China, as it shielded the heartland region around the imperial capital. The pass' strategic location dictated that without mounting a costly direct siege, the only way an invading army can get past the pass' defense was to circumvent it around the north through a few treacherously narrow mountain passes deep within the Yan Mountains, which would make it very difficult to maintain supply lines and thus any sizeable invasions. This defensive significance therefore earned the pass the famous nickname "Greatest Pass Under Heaven" (天下第一关).

The GIUK gap (sometimes written G-I-UK) is an area in the northern Atlantic Ocean that forms a naval choke point. Its name is an acronym for Greenland, Iceland, and the United Kingdom, the gap being the two stretches of open ocean among these three landmasses. It separates the Norwegian Sea and the North Sea from the open Atlantic Ocean. The term is typically used in relation to military topics. The area has for some nations been considered strategically important since the beginning of the 20th century.

Hangu Pass or Hanguguan was a fortified gateway that commanded the strategic mountain pass between the Yellow River and Qinling Mountains, forming the main choke point on the only land corridor between the Central Plain and the Guanzhong region. The pass restricted access into the lower Wei River valleys, where the heartland of the state of Qin and the unified Qin dynasty were located, as well as the subsequent dynasties of Han, Sui and Tang.

The Hangu Pass lies on the south (right) bank of the Yellow River, 60 km (37 mi) downstream of its eastward bend out of the Ordos Loop. It was built by the state of Qin in 330 BC and had been the site of many sieges and field battles during the Warring States period and early imperial eras. Due to terrain changes from bank erosions and alluvial deposition of the Yellow River over the centuries, the Hangu Pass eventually fell to ruins after losing its defensive values to the newer Tong Pass to its west, which was built near the mouth of the Wei River in 196 AD by the warlord Cao Cao.

The Khyber Pass is a mountain pass in the Khyber Pakhtunkhwa province of Pakistan, on the border with the Nangarhar Province of Afghanistan. It connects the town of Landi Kotal to the Valley of Peshawar at Jamrud by traversing part of the White Mountains. Since it was part of the ancient Silk Road, it has been a vital trade route between Central Asia and the Indian subcontinent and a strategic military choke point for various states that controlled it. The Khyber Pass is considered one of the most famous mountain passes in the world.