If strength is to be found in numbers, more than three million French people defeated a few tens of thousands of extremist followers of Islamic State and al-Qaeda in the Arabian Peninsula when they marched across Paris and dozens of French towns yesterday.

The interior ministry estimated that more than 1.5 million marched in Paris – the biggest demonstration since the capital was liberated in August 1944.

At the same time, some 1.2 million marched in towns and cities across France. A quarter of the population of Bordeaux marched. Ten thousand turned up in Dammartin-en-Goele, more than the usual population of the small town where Chérif and Said Kouachi were killed on Friday.

They poured into the Place de la République in Paris from every direction, then waited patiently, packed like sardines, for two hours, then inched along, starting and stopping, as the march moved at glacial speed towards the Place de la Nation.

The boulevards became a human ocean from which occasional chants rose of “Char-lie. Char-lie”, followed by rhythmic applause. When a few drops of icy rain fell, a woman told me that heaven was weeping for the 17 French people killed in three days by the Kouachi brothers and their accomplice Amedy Coulibaly.

Sadness, anger, fear

"I was glued to the television for 48 hours," recounted Carole Leclerc (56). "I feel sadness, and anger, and fear. I'm afraid there will be more attacks, because they are crazy and nothing can stop them. I know there's a risk they'll attack the march, but I needed to march today. I couldn't look at myself in the mirror if I didn't."

Philippe Ghielmetti (54) was the saddest person I met on the march. A designer for Les Échapées, the publishing house owned by Charlie Hebdo, Ghielmetti knew all the magazine employees massacred on January 7th, and was close to the cartoonists Tignous and Charb.

“There are no limits to stupidity and hatred,” Ghielmetti said, with tears in his eyes. He wouldn’t have been surprised by a beating, or a Molotov cocktail. “But what happened was unimaginable.”

Like Leclerc and everyone I spoke to, Ghielmetti felt it was necessary to participate in the march – "because we are human beings, because 17 people died for nothing". He was surprised by the outpouring of international solidarity. "Charlie had 35,000 readers and it was unknown even to most French people. It became a symbol from one hour to the next."

And like other marchers, Ghielmetti doubted France had seen the last of extremist violence.

“On November 22nd, Islamic State appealed to ‘all Muslims worthy of the name’ to carry out attacks wherever they are. Before last week, over the holidays, four cars drove into crowds of people.”

Rémy (66), a retired scientist who specialised in air pollution, made his own sign. He crossed out the names “Allah,” “Dieu,” and “Yahweh”, leaving only the words “You”, “Me” and “Us”.

“We don’t need God,” Rémy said. “He’s created only problems until now. The religious wars have been the bloodiest.”

Echoing the prophecy of the French writer André Malraux that the 21st century would be the century of religion, he added: “We’re in a period of religious war now: Sunni versus Shia; extremist Catholics who marched against same-sex marriage; Islamists against secularists . . . ”

Choice of guests

President François Hollande headed the march with some 40 heads of state and government, including Angela Merkel and David Cameron. Some marchers were offended by Hollande's choice of guests.

"The Turkish government lets jihadis transit its territory to reach Syria, " said Ben (58), a photographer and the son of Algerian immigrants, alluding to the presence of prime minister Ahmet Davutoglu.

“They are ambivalent about Islamic State and mistreat the Kurds.”

Mohammed Henniche, the president of the Union of Muslim Associations, said the presence of Israeli prime minister Benjamin Netanyahu was “a big problem for a lot of Muslims”.

“If Netanyahu wanted peace, he would have made it a long time ago,” Ben said. “He has a lot of blood on his hands, but I came anyway, because we have to be here, for humanity, for dignity.”

Jorge Dillais (19), a hotel school student and the son of Brazilian immigrants, made a sign saying "Nous sommes Charlie. Vive l'Islam." Lest anyone misunderstand, the flip side of the placard said "Stop the extremists."

“What I meant was that I don’t want us to become Islamophobes because of what happened,” Dillais explained. “I phoned everyone I knew and told them to come. So many of them said ‘I’m afraid.’

The people who are here today are strong. We're here to show that we're not afraid, and that Charlie isn't dead."