CAIRO (NYTIMES) - The 193km artificial waterway known as the Suez Canal has been a potential flashpoint for geopolitical conflict since it opened in 1869.

Now the canal, a vital international shipping passage, is in the news for a different reason: A 400m-long, Japanese-owned container ship en route from China to Europe has been grounded in the canal for days, blocking more than 100 vessels and sending tremors through the world of maritime commerce.

With the rescue mission expected to extend into weeks, the stricken Ever Given is forcing other container ships to take detours around Africa that would add 9,656km to the journey and about US$300,000 (S$404,190) in fuel costs.

Dredgers will need to move between 15,000 and 20,000 cubic metres of sand in order to reach a depth of 12 to 16 metres - eight times the size of an Olympic swimming pool - to allow the ship to float, the Suez Canal Authority said on Thursday.

Here are some basics on the history of the canal, how it operates, how the vessel got stuck and what it means.

Q: Where is the Suez Canal?

A: The canal is in Egypt, connecting Port Said on the Mediterranean Sea to the Indian Ocean via the southern Egyptian city of Suez on the Red Sea.

The passage enables more direct shipping between Europe and Asia, eliminating the need to circumnavigate Africa and cutting voyage times by days or weeks.

The canal is the world's longest without locks, which connect bodies of water at differing altitudes. With no locks to interrupt traffic, the transit time from end to end averages about 13 to 15 hours, according to a description of the canal by GlobalSecurity.org.

Q: Who built the Suez Canal and when?

A: The canal, originally owned by French investors, was conceived when Egypt was under the control of the Ottoman Empire in the mid-19th century.

Construction began at the Port Said end in early 1859, the excavation took 10 years, and the project required an estimated 1.5 million workers.

According to the Suez Canal Authority, the Egyptian government agency that operates the waterway, 20,000 peasants were drafted every 10 months to help construct the project with "excruciating and poorly compensated labour". Many workers died of cholera and other diseases.

Political tumult in Egypt against the colonial powers of Britain and France slowed progress on the canal, and the final cost was roughly double the initial US$50 million projected.

Q: Which country controls the canal now?

A: The British powers that controlled the canal through the two World Wars withdrew forces there in 1956 after years of negotiations with Egypt, effectively relinquishing authority to the Egyptian government led by then President Gamal Abdel Nasser.

Q: What was the "Suez Crisis" that nearly led to war?

A: The crisis began in 1956 when Egypt's president nationalised the canal after the British departed. He took other steps that were deemed security threats by Israel and its Western allies, leading to a military intervention by Israeli, British and French forces.

The crisis briefly closed the canal and raised the risk of entangling the Soviet Union and the United States.

It ended in early 1957 under an agreement supervised by the United Nations, which sent its first peacekeeping force to the area. The outcome was seen as a triumph for Egyptian nationalism, but its legacy was an undercurrent in the Cold War.

The Suez Crisis was also a theme in Season 2, Episode 1 of The Crown, the acclaimed Netflix series about Britain's royals, as the British prime minister at the time, Mr Anthony Eden, struggled over how to respond.

Q: Was the Suez Canal designed to handle the huge vessel that grounded?

A: The beached vessel, the Ever Given, which is operated by the Evergreen Shipping line, is one of the world's largest container ships, about the length of the Empire State Building.

Although the canal was originally engineered to handle much smaller vessels, its channels have been widened and deepened several times, most recently six years ago at a cost of more than US$8 billion.

Q: What led to the vessel's grounding, and what's being done about it now?

A: Poor visibility and high winds, which made the Ever Given's stacked containers act like sails, are believed to have pushed it off course and led to its grounding.

Salvagers have tried a number of remedies: pulling it with tugboats, dredging underneath the hull and using a front-end loader to excavate the eastern embankment, where the bow is stuck. But the vessel's size and weight, 200,000 metric tonnes, had frustrated salvagers as at Thursday (March 25) night.

Some marine salvage experts have said nature might succeed where tugs and dredgers have failed. A seasonal high tide on Sunday or Monday could add roughly 45cm of depth to the canal, perhaps floating the ship.

Q: What are the ramifications if the Ever Given remains stuck?

A: That depends on how long the canal, which is believed to handle about 10 per cent of global maritime commercial traffic, is closed.

TradeWinds, a maritime industry news publication, said that with more than 100 ships waiting to traverse the canal, it could take more than a week just for that backlog to clear.

A prolonged closure could be hugely expensive for the owners of ships waiting to transit the canal. Some may decide to cut their losses and reroute their vessels around Africa.

The owner of the Ever Given is already facing millions of dollars in insurance claims and the cost of emergency salvage services.

Egypt's government, which received US$5.61 billion in revenue from canal tolls in 2020, also has a vital interest in refloating the Ever Given and reopening the waterway.