RAQQA, Syria (AP) -- Hunkered down in sniper positions on the top floor of an abandoned building in the Syrian city of Raqqa, two Americans and a British volunteer face off Islamic State snipers on the other side of the front line. The trio, including two who were battle-hardened by experience in the French Foreign Legion and the war in Iraq, have made the war against IS in Syria their own.
They are among several U.S. and British volunteers in the decisive battle against the Islamic State group for Raqqa, the city in northeastern Syria that the militants declared the capital of their self-proclaimed caliphate in parts of Syria and neighboring Iraq.
The men joined U.S.-allied Syrian militias for different reasons -- some motivated by testimonies of survivors of the unimaginable brutality that IS flaunted in areas under its control.
Others joined what they see as a noble quest for justice and a final battle with the "heart of darkness," in a belief that violence can only be met with violence.
Taylor Hudson, a 33-year old from Pasadena, compares the fight for Raqqa to the 1945 Battle of Berlin in World War II that was critical to ending the rule of Adolf Hitler.
"This is the Berlin of our times," said Hudson, who doubles as a platoon medic and a sniper in the battle against the militants. For him, IS extremists "represent everything that is wrong with humanity."
Syria's war, now in its seventh year, has attracted foreign fighters to all sides of the complicated conflict.
Islamic extremists from Europe, Asia and North Africa have boosted the ranks of the Islamic State group, as well as rival radical al-Qaida-linked groups. Shiite Iranian and Lebanese militias have sided with the Syrian government, deepening the sectarian nature of the conflict that has killed over 400,000 people and displaced over 11 million, half of Syria's pre-war population.
On the anti-IS side -- though far less in numbers than the thousands of foreigners who swelled the IS ranks -- most Western foreign volunteers have been drawn to the U.S.-allied Kurdish militia known as The People's Protection Units, or by their Kurdish initials as the YPG. The U.S. military has developed a close relationship with the YPG and its extension, the Syrian Democratic Forces, in the war against IS.
Some Western volunteers have died in battle -- earlier in July the YPG announced that 28-year-old Robert Grodt, of Santa Cruz, California, and 29-year-old Nicholas Alan Warden, of Buffalo, died in the battle for Raqqa.
Since launching the push on Raqqa on June 6, the U.S.-backed forces have conquered a third of the city.
Hudson, who has been fighting in Syria for the past 13 months, said he was moved to tears by stories in the media of Iraqi Yazidi women who were enslaved by IS militants and looked for a way to help. A pharmacy student who learned combat medicine in the field, he said he had treated some 600 wounded ahead of the march onto Raqqa.
The presence of Western anti-IS volunteers in Syria has created something of a conundrum for their governments, which have often questioned them on terrorism charges.
"I am not a terrorist," said Macer Gifford, a 30-year former City broker in London, who came to Syria three years ago to volunteer first with the Kurdish militia. Now he is fighting with an Assyrian militia, also part of the U.S-backed forces battling IS militants.
"I am here defending the people of Syria against terrorists," he added.
Gifford has been questioned by both his British government and by the U.S government. At home, he has written and lectured about the complex situation in Syria, offering a first-hand experience of IS' evolving tactics.
He believes the militants can only be defeated by sheer force.
"The Islamic State (group) is actually an exceptional opponent," Gifford said. "We can't negotiate them away, we can't wish them away. The only way we can defeat them is with force of arms."
For Kevin Howard, a 28-year old former U.S. military contractor from California who fought in Iraq in 2006, the war against the Islamic State group is more personal.
A skilled sniper who prides himself in having killed 12 IS militants so far, Howard said he is doing it for the victims of the Bataclan theatre in France, where the sister of one of his best friends survived. The Nov. 13, 2015 attacks claimed by IS killed 130 people at Paris cafes, the national stadium and the Bataclan, where 90 died.
"This is a continuation of that fight, I think if you leave something unfinished, it will remain unfinished for a lifetime," he said, showing off his 1972 sniper rifle.
On his forehead and neck, he has tattooed the "Rien N'empche" -- or "Nothing Prevents"-- words from the song of the French Foreign Legion in which he served, and "life is pain."
"For me this is a chance to absolutely go to the heart of darkness and grab it and get rid of it," he added.
From his sniper position on Raqqa's front line, he peeked again through the rifle hole. For Howard, the orders to march deeper into the IS-held city can't come soon enough.