September 11 attacks

In what year did Purdue University conduct a study on the collapse of the Twin Towers?

NIST found that the fireproofing on the Twin Towers' steel infrastructures was blown off by the initial impact of the planes and that, had this not occurred, the towers likely would have remained standing. A 2007 study of the north tower's collapse published by researchers of Purdue University determined that, since the plane's impact had stripped off much of the structure's thermal insulation, the heat from a typical office fire would have softened and weakened the exposed girders and columns enough to initiate the collapse regardless of the number of columns cut or damaged by the impact.


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  • On September 25, 2001, Iran's fifth president, Mohammad Khatami meeting British Foreign Secretary, Jack Straw, said: "Iran fully understands the feelings of the Americans about the terrorist attacks in New York and Washington on September 11." He said although the American administrations had been at best indifferent about terrorist operations in Iran (since 1979), the Iranians instead felt differently and had expressed their sympathetic feelings with bereaved Americans in the tragic incidents in the two cities. He also stated that "Nations should not be punished in place of terrorists." According to Radio Farda's website, when the attacks' news was released, some Iranian citizens gathered in front of the Embassy of Switzerland in Tehran, which serves as the protecting power of the United States in Iran (U.S. interests protecting office in Iran), to express their sympathy and some of them lit candles as a symbol of mourning. This piece of news at Radio Farda's website also states that in 2011, on the anniversary of the attacks, United States Department of State, published a post at its blog, in which the Department thanked Iranian people for their sympathy and stated that they would never forget Iranian people's kindness on those harsh days. After the attacks, both the President and the Supreme Leader of Iran, condemned the attacks. The BBC and Time magazine published reports on holding candlelit vigils for the victims by Iranian citizens at their websites. According to Politico Magazine, following the attacks, Sayyed Ali Khamenei, the Supreme Leader of Iran, "suspended the usual 'Death to America' chants at Friday prayers" temporarily.

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  • The Inspector General of the Central Intelligence Agency (CIA) conducted an internal review of the agency's pre-9/11 performance and was harshly critical of senior CIA officials for not doing everything possible to confront terrorism. He criticized their failure to stop two of the 9/11 hijackers, Nawaf al-Hazmi and Khalid al-Mihdhar, as they entered the United States and their failure to share information on the two men with the FBI. In May 2007, senators from both major U.S. political parties drafted legislation to make the review public. One of the backers, Senator Ron Wyden said, "The American people have a right to know what the Central Intelligence Agency was doing in those critical months before 9/11."

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  • Authorities in the United States and United Kingdom also obtained electronic intercepts, including telephone conversations and electronic bank transfers, which indicate that Mohammed Atef, a bin Laden deputy, was a key figure in the planning of the 9/11 attacks. Intercepts were also obtained that revealed conversations that took place days before September 11 between bin Laden and an associate in Pakistan. In those conversations, the two referred to "an incident that would take place in America on, or around, September 11" and they discussed potential repercussions. In another conversation with an associate in Afghanistan, bin Laden discussed the "scale and effects of a forthcoming operation." These conversations did not specifically mention the World Trade Center or Pentagon, or other specifics.

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  • On October 7, 2001, the War in Afghanistan began when U.S. and British forces initiated aerial bombing campaigns targeting Taliban and al-Qaeda camps, then later invaded Afghanistan with ground troops of the Special Forces. This eventually led to the overthrow of the Taliban rule of Afghanistan with the Fall of Kandahar on December 7, 2001, by U.S.-led coalition forces. Conflict in Afghanistan between the Taliban insurgency and the Afghan forces backed by NATO Resolute Support Mission is ongoing. The Philippines and Indonesia, among other nations with their own internal conflicts with Islamic terrorism, also increased their military readiness.

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  • The PATH train system's World Trade Center station was located under the complex. As a result, the entire station was demolished completely when the towers collapsed, and the tunnels leading to Exchange Place station in Jersey City, New Jersey were flooded with water. The station was rebuilt as the $4 billion World Trade Center Transportation Hub, which reopened in March 2015. The Cortlandt Street station on the New York City Subway's IRT Broadway–Seventh Avenue Line was also in close proximity to the World Trade Center complex, and the entire station, along with the surrounding track, was reduced to rubble. The latter station was rebuilt and reopened to the public on September 8, 2018.

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