HAMBURG, Germany (AP) — President Donald Trump was met with thousands of protesters when he arrived at meetings in Brussels in May. But with Russian President Vladimir Putin and Turkish President Recep Tayyip Erdogan joining him at the Group of 20 meetings in Germany this week, Trump is unlikely to be the only target for demonstrators.
Add India's Prime Minister Narendra Modi, Chinese President Xi Jinping and other leaders whose policies have sparked unrest to the cauldron that is Hamburg — the summit venue is a short walk from a notorious hotbed of left-wing protest — and the brew could prove explosive.
"G-20: Welcome to Hell" is the slogan anti-globalization activists have registered for their protests on July 6, when Trump and other leaders arrive for the July 7-8 summit in the northern port city.
"We are calling on the world to make Hamburg a focal point of the resistance against the old and new capitalist authorities," said the organizers, who have ties to the Rote Flora squat, a center for radical leftists where police have clashed frequently with protesters.
The site is about a kilometer (less than a mile) from where the leaders will be meeting.
In the weeks leading up to the summit, police cars have been burned and train lines have been sabotaged. Authorities in Hamburg and the nearby city of Rostock have confiscated improvised weapons such as fire-extinguishers filled with flammable liquid, baseball bats and other items in several raids.
"We have to assume that this is only a tiny percentage of what is still in basements and garages in and around Hamburg," Hamburg police criminal director Jan Hieber told reporters this week.
The "Welcome to Hell" demonstration is just one of dozens of protests that have been registered under a smorgasbord of themes — including a far-right pro-Trump rally — with more than 100,000 demonstrators from across Europe and beyond expected to take part.
Officials estimate that some 8,000 protesters from Europe's violent left-wing scene to be on hand and have been tracking known activists coming in from Scandinavia, Switzerland, Italy and elsewhere, Hamburg police chief Ralf Martin Meyer said.
"This isn't about sit-ins," Meyer said.
In a preview of things likely to come, police clashed in Hamburg with hundreds of protesters Tuesday night, using pepper spray and water cannons to eventually bring the crowd under control.
That's not to say all protesters are violent — most aren't and see the gathering as an opportunity to highlight their messages with the world watching and in hopes the assembled leaders will listen.
Greenpeace, for example, regards the G-20 as a chance for the leaders to send a strong signal about fighting climate change — despite the Trump administration's decision to pull out of the Paris agreement on reducing emissions.
"We're looking for the G-20, and if that's not possible, then the G-19, to go forward with implementing the Paris agreement and maybe doing even more," Greenpeace International's executive director Jennifer Morgan told The Associated Press.
Like many nonprofits, Greenpeace is fighting a security decision to block off a 38-square-kilometer (almost 15-square-mile) "no-protest zone" encompassing the airport where leaders will arrive and the conference center where they will meet.
The group is calling for residents who live within the security zone to hang flags and banners out of their windows so the world leaders will see them on the way in.
"Greenpeace stands for nonviolent direct action — we have peace in our name — and it would be a shame if violence moved the message away from what the G-20 should be doing on climate and other issues," Morgan said.
A protest on Wednesday featured hundreds of people painted as clay figures — meant to represent a society that has lost its belief in solidarity — shedding their gray costumes.
German Chancellor Angela Merkel has told community organizers in Hamburg that she understood the importance of demonstrations to express criticism and concerns, but urged them to remain non-violent.
"It should be peaceful criticism," she said in June.
Still, German security officials are preparing for the worst, drawing upon decades of experience dealing with violent May Day demonstrations and other protests at major events, including the G-7 in 2015 and G-8 in 2007.
In addition to the no-protest zone, tightly secured transit corridors were set up to ensure that convoys will be able to keep moving so they don't become targets for violent demonstrators or extremist attacks.
Germany has also denied Erdogan permission to hold a rally on the sidelines of the summit, which could have drawn huge protests from Kurds living in Germany.
Hamburg is boosting its police force with reinforcements from around the country and will have 20,000 officers on hand to patrol the city's streets, skies and waterways.
"You can be certain that you will see all of the equipment that German police have here in Hamburg," said Hartmude Dudde, who is leading the security team for Hamburg police. That includes both underwater and aerial drones.
Germany's counter-terrorist GSG9 force will be assisted by Austria's counterpart Cobra and specialists from the Netherlands and other countries, Meyer said. They'll be stationed around the city in strategic locations to help protect the summit's expected 6,500 participants from any attack.
"You can count on a very quick reaction time," Meyer told reporters. "Well under a minute, that's the concept. They are, in principle, everywhere."
Demonstrations need to be registered with authorities in Germany before going ahead — otherwise they're considered illegal and can be immediately broken up. That means that police can be expected to react swiftly to any "spontaneous" protests inside the security zone closer to where the world leaders are meeting.
On the outskirts of the city, a former wholesale supermarket has been converted into a special temporary prison with holding cells for 400 people, and judges on hand to decide whether there's enough evidence to keep them longer term or to set them free.
"Peaceful protest is welcome in our democracy... but violent protest will be stopped," Germany's top security official, Interior Minister Thomas de Maiziere, said this week.
"This event will not be disturbed, of that I am certain," he said.