In 2019, 13,826 people around the world were killed in acts of terrorism. Over half of those deaths were at the hands of just four groups - The Taliban, Boko Haram, ISIS and Al Shabab and their affiliates.
Despite the high death toll, the Global Terrorism Index found total deaths from terrorism fell for the fifth consecutive year. One hundred and three countries saw a reduction in violence while the situation in 35 countries got worse, the report found.
In the Middle East and North Africa, terrorism-related deaths fell by 87 per cent since 2016, the lowest levels since 2003.
With the coronavirus pandemic keeping many at home this year and with ISIS' physical territory practically gone, the internet has been their tool of choice for spreading extremist, fear-mongering and violent ideologies, the report from the The Institute for Economics and Peace (IEP) found
Here's what you need to know about the world's worst terrorist groups:
The Taliban remained the world's deadliest terrorist group in 2019, killing at least almost 5,000 people.
The Taliban rose in 1994 out of the fight against the Soviet invasion of Afghanistan. With the collapse of the Russian-backed government, the group took over the capital and ruled the country after 1996. However, their harbouring of Osama bin Laden and his Al Qaeda group brought about the US invasion in 2003 in response to the 9/11 attacks that killed over 3,000 people.
The Taliban is a collection of factions that operate under a banner. They have waged a bloody insurgency against international forces for nearly two decades and battled the Kabul government.
Today, the Taliban still controls over 50 per cent of the country, despite billions in aid and military spending to try and dislodge the group and bolster the rule of the Afghan government.
While the number of people the group killed in 2019 was down 18 per cent on 2018, the number of attacks they carried out rose 5 per cent to 1,025.
The United States Institute for Peace estimates that the group is now 60,000 fighters strong.
Affiliates: Pakistan-based Tehrik-i-Taliban Pakistan (TTP) killed 73 people in 30 attacks in Pakistan last year which shows the Taliban had expanded its presence.
Tactics: Half the people killed and targeted by the Taliban last year were military and security forces. Civilian deaths fell by 31 per cent but bombings went up by 49 per cent from 2018.
After 19 years of fighting the US, the group signed an agreement with the Washington that will see international troops leave in exchange for a reduction in violence, talks with Kabul, a prisoner swap and a halt to attacks on coalition forces.
Taliban attacks on American troops have largely dried up, but they continue to launch regular attacks on security forces but deny hitting civilian targets like universities and schools.
While talks between the Taliban and Kabul are ongoing, women's rights groups worry about a return of the hardline conservatives to rule as it could erase the small gains made for female empowerment in the last 20 years.
Founded in 2009, the group sought out to create a so-called "caliphate" in northeast Nigeria.
In 2015, the group pledged allegiance to ISIS and intensified their violent operations.
After years of dwindling activity, Nigeria-based Boko Haram’s attacks spiked in 2019, increasing by just under 50 per cent. They targeted mostly military units but also caused civilian deaths, making them the deadliest group in sub-Saharan Africa.
The extremist militant group spread into Chad, Cameroon and Niger, sparking international condemnation for kidnapping schoolgirls from Nigeria’s Chibok in 2014.
Amnesty International says that the group has kidnapped civilians to be used as sex slaves, fighters, suicide bombers and cooks.
Terror-related deaths attributed to Boko Haram increased by 46 per cent in 2019 over the previous year. Terror incidents linked to the group increased by 43 per cent. But the number of deaths caused by the group continued to decrease from the peak in 2014 and remain six times lower than the high.
Of the 1,068 deaths attributed to Boko Haram in 2019, 69 per cent occurred in Nigeria. While the number of deaths in Nigeria dropped, the numbers killed in Niger and Chad continued to increase.
Niger recorded a 176 per cent increase in terrorism deaths attributed to Boko Haram in 2019, the report found.
The group’s deadliest attack of the year was in Cameroon when several hundred fighters armed with rocket launchers attacked a military post in Darak in the country's north. The attack killed over 101, including 37 soldiers and civilians.
Despite a 46 per cent increase in deaths and a 43 per cent rise in attacks, Boko Haram is still not as deadly than its height of power in 2014, with 70 per cent of killings happening in Nigeria.
The terror group killed its second highest number of people in Cameroon although deaths in Nigeria fell but increased in Niger.
Affiliates: In 2016, the group broke up forming multiple off-shoots. The largest of these is the IS West Africa Province (ISWAP) - comprised of anywhere between 3,500 to 5,000 fighters by UN estimates. The group claimed ruthless attacks on civilians and military bases.
Tactics: Boko Haram changed its violent methods from suicide bombings and explosions to armed assaults and kidnappings, resulting in a decline in the overall fatality of their attacks from 15 deaths per incident in 2014 to just four per attack in 2019.
Although a counter-terrorism force exists in tandem with the Nigerian military, it had not successfully reclaimed areas of control from Boko Haram. The group continues to control parts of Nigeria's north-east, blocking humanitarian aid and government services.
Following territorial defeats in Iraq’s Mosul and Syria’s Raqqa in 2017 and 2019, ISIS was the third deadliest terrorist group in 2019 but experts agree that its ideologies remain alive online.
It was formed by Al Qaeda members and “disaffected former members of the US-trained Sons of Iraq that supported US operations to dismantle Al Qaeda in Iraq before the 2010 withdrawal," the report said.
Since 2014, ISIS killed over 30,000 people, the majority of whom were in Iraq.
Deaths perpetrated by ISIS are at their lowest since 2013 and continued to drop from 1,571 in 2018 to 942 in 2019 after virtually all of their territory was recaptured in counter-terrorism operations.
The group's leader Abu Bakr Al Baghdadi was killed in a 2019 US operation,
The group utilises affiliates to carry out attacks in Iraq and Syria but deaths caused by the group continued to fall from 2017-2019, the IEP report said.
Affiliates: Most significantly, the Khorasan Chapter in south Asia, the Islamic State in the Greater Sahara in sub-Saharan Africa and the Central Africa Province of the Islamic State which were the sixth, 11th and 12th deadliest groups of the year.
Tactics: More than half of ISIS attacks were through bombings and explosions, followed by armed assaults, killing 687 and 114 people in 2019. ISIS civilian deaths also went down by over 80 per cent.
Future: Although overall attacks and deaths declined in 2019, the group expanded its operations across seven countries. ISIS carried out the year's deadliest attack in Sri Lanka where eight suicide bombers carried out co-ordinated assaults on hotels and churches killing 266 people, injuring at least 500 others.
The group emerged in 2006 as an Al Qaeda affiliate and has between 7,000 and 9,000 fighters. It controls large areas in southern and central Somalia and has launched attacks on the capital and the international airport where embassies are located.
The number of people killed by Al Shabab fell only by eight per cent from 2018, at 578 deaths - almost 90 per cent of those in Somalia, and the remainder in Kenya. But the number of incidents did fall 40 per cent compared with 2018.
Mogadishu has long been the epicentre of terrorist activity by Al Shabab and in 2019 over half of the group's attacks in Somalia occurred in Mogadishu, causing 280 fatalities, the report found.
Attack lethality against civilians became went up in 2019 from 1.9 deaths per attack in 2018 to 3.2 deaths per attack in 2019.
In Kenya terrorism deaths attributed to Al Shabab increased by 83 per cent in 2019, the majority in Nairobi. This was led by the attack on the DusitD2 hotel in Nairobi where at least 21 civilians were killed.
Al Shabab is Al Qaeda's Somalia and Kenya-based affiliate comprised of 7,000 to 9,000 fighters, the IEP estimates.
Bombings, armed assaults and assassinations mark Al Shabab's most used modes of attack. Civilians were targeted in the majority of attacks on Somalia and Kenya.