The Straits Times looks at 20 years of securing Singapore following the Sept 11 attacks.
Sept 11, 2001: A series of coordinated attacks through hijacked planes by Al-Qaeda against the United States takes place, resulting in the deadliest terrorist attack in history.
Dec 9, 2001: Six Singaporean Jemaah Islamiah (JI) members are arrested by the Internal Security Department, with 15 more detained within a month, for being involved in plans to attack Yishun MRT station and several foreign embassies in Singapore.
2002: The Inter-Racial and Religious Confidence Circles are set up to promote racial and religious harmony at the grassroots level.
February 2002: The Inter-Agency Aftercare Group is formed to oversee the social rehabilitation and reintegration of radicalised individuals.
February 2003: The Indonesian authorities arrest Mas Selamat Kastari, chief of JI's Singapore operations.
April 2003: The Religious Rehabilitation Group is launched to rehabilitate detained JI members and their families through counselling.
August 2005: The Police MRT Unit, which later became the Public Transport Security Command, was formed to enhance the security of Singapore's public transport system.
February 2006: The Community Engagement Programme, predecessor to the SGSecure movement, is launched. Its aim is to strengthen intercommunal ties in the event of an incident that could affect social cohesion.
From 2007: Former lawyer Abdul Basheer Abdul Kader, who had made plans to join the Taliban in Afghanistan, is believed to be the first self-radicalised detainee who was influenced by social media.
2007 to 2013: The Singapore Armed Forces deploy close to 500 personnel to Afghanistan, as part of the International Security Assistance Force.
February 2008: Escape of Mas Selamat, who had allegedly plotted to hijack a plane and crash it into Changi Airport, from Whitley Road Detention Centre. He was recaptured in May 2009 in Malaysia.
May 2010: Indonesian investigators discover a map of Singapore's MRT network, with Orchard station circled, along with a street map of the shopping belt, in the home of a killed terror suspect.
2014: The number of detentions of JI members tails off. Detainees are increasingly self-radicalised.
April 2015: A 19-year-old teenager becomes the first known youth to harbour the intention to carry out violent attacks in Singapore, and is detained under the Internal Security Act. He had planned to join ISIS after viewing terrorist propaganda online.
November 2015: Singapore uncovers its first radical Islamist terror cell comprising foreigners, with the arrests and deportation of 27 Bangladeshis working in the construction industry.
2016: The police's Emergency Response Teams are formed to act as the first line of response to a terrorist attack. They perform patrols in public areas as a deterrent measure.
August 2016: Arrest of a terror cell in Indonesia for plotting to fire a rocket at Marina Bay Sands from Batam.
September 2016: Launch of the SGSecure movement to train and mobilise the community against terror attacks.
October 2016: The police stage one of their largest counter-terrorism drills, code-named Exercise Northstar, involving more than 3,200 personnel from various agencies.
June 2017: The Ministry of Home Affairs releases its first Singapore Terrorism Threat Assessment Report. It notes that the Republic is a key target for terrorists.
June 2017: A 22-year-old childcare assistant becomes the first woman detained in Singapore for her radicalism.
September 2017: The first known ISIS recruitment video to feature a Singaporean surfaces, with Megat Shahdan Abdul Samad calling on regional militants to join the fight in Syria.
December 2020: A self-radicalised 16-year-old Protestant Christian male is detained after plotting to attack two mosques on the second anniversary of New Zealand's Christchurch attacks. He is the first detainee to be influenced by far-right extremist ideology.
March 2021: A self-radicalised 20-year-old Muslim male is detained after planning to attack Jews at the Maghain Aboth Synagogue in Waterloo Street.