Both tankers were born in Nagasaki in 1973, products of a shipbuilding boom driven by surging global demand for oil transport. Mitsubishi Heavy Industries began work on the Venoil in October 1972 and the Venpet in January 1973, completing them in March and June of that year at a cost of approximately US$28 million each. At more than 330,000 deadweight tonnes, they were classified as Very Large Crude Carriers -- the workhorses of the 1970s oil trade, built to shuttle crude between the Persian Gulf and the industrial economies of North America and Europe. Both ships were registered in Liberia, owned and operated by the Bethlehem Steel Corporation, and crewed by Taiwanese sailors. They were, in nearly every measurable way, identical.

On that December morning, the Venoil was headed for Halifax, Nova Scotia, carrying between 250,000 and 307,000 tonnes of crude oil loaded at Iran's Kharg Island terminal. The Venpet, running in ballast, was on the return trip to Kharg Island after unloading her cargo at Halifax. Fog had reduced visibility to less than 370 meters. Both ships were tracking each other on radar, but they had accepted a closest point of approach of only one mile -- dangerously narrow for vessels of their size in near-zero visibility, without accounting for radar errors in range and bearing. When they realized the gap was closing, both ships turned in the same direction to increase distance, a mirrored maneuver that instead brought them together. The Liberian marine board's investigation, published in 1985, concluded that the collision resembled the 1956 disaster between the Andrea Doria and the Stockholm: two ships, both aware of each other, both maneuvering, both doing precisely the wrong thing.

The collision ruptured the Venpet's forward fuel tank and two of the Venoil's crude oil storage tanks. Bunker oil and heavy crude poured into the sea and ignited. The total spill was estimated at between 26,600 and 30,500 tonnes, though some of the oil was consumed by the flames that engulfed both vessels. The majority of the Venoil's crew launched a lifeboat, but thirteen men were trapped by fire and had to be rescued by helicopter. Two crew members died. The British bulk carrier Jedforest and the merchant ship Clan Menzies, passing through the area, rescued the remaining crews. Patches of emulsified oil spread into a 160-kilometer-wide slick, part of which reached shore, fouling over 130 kilometers of coastline from Plettenberg Bay to Stilbaai.

The burning, abandoned tankers drifted toward shore as their fires gradually died. Salvage teams towed them into the Agulhas Current to prevent grounding, using the powerful southwestward current to carry any further oil releases away from the coastline. The Venpet reached Algoa Bay for repairs on Christmas Eve, 1977. The Venoil, which had drifted 250 miles southwest into the current, arrived on New Year's Day 1978. Her remaining crude was transferred to the tanker Litiopa before she sailed to Halifax. Both damaged ships eventually returned to Japan -- to Sasebo and Nagasaki -- for extensive repairs at the same yards that had built them.

Neither ship survived long. The Venoil was renamed Resolute in 1981 and Opportunity in 1983 before being scrapped at Ulsan, South Korea, in October 1984 -- eleven years after her launch. The Venpet, renamed Alexander The Great in 1980, met a more violent end. In June 1984, while moored at the Kharg Island oil terminal where she had loaded and unloaded so many times, she was struck by an Iraqi Exocet missile during the Iran-Iraq War. The damage was catastrophic, and she was towed to Kaohsiung, Taiwan, for scrapping that October. Two ships, built together, registered together, crewed together, and in the end, destroyed within months of each other -- mirror images to the last.