BANGKOK, Thailand — The ragtag militants who stormed one of the Philippines’ major cities to carve out a new nation — an imagined state they call “Bangsamoro Republik” — must have known they were on a suicide mission.

Following their initial Sept. 9 assault, armed rebels from the Moro National Liberation Front (MNLF) still occupy districts in Zamboanga City, an island hub with 800,000-plus inhabitants that’s roughly equal in population size to San Francisco. They have since detained the police chief as a “prisoner of war” — later freeing him — and sent 10 percent of the city dwellers fleeing, according to Human Rights Watch.

The rebels’ days, however, appear numbered.

From their initial estimated force strength of several hundred men, according to the Philippine Inquirer, they are down 135 fighters: 71 killed, 64 captured.

They have incurred the wrath of at least 5,000 troops with the Philippine armed forces, which routinely receive close tactical support from the US military. Government troops have hammered rebel positions with helicopter-borne rocket strikes and artillery rounds.

This is the latest carnage to result from a complex and extremely bloody conflict — 120,000 dead over four decades, according to most estimates — that pits outgunned Islamic militants against the US-backed, Catholic-dominated Philippine government.

As a Filipino journalist for major Manila-based outlet GMA News wrote recently from the scene of the carnage: “The devastation and loss of life caused by the MNLF are unforgivable, whatever motive and belief behind it. But one cannot help feeling a sense of awe at the determination of these men.”

Their motive, according to the rebels’ own rhetoric, is ridding their tropical, Muslim-majority island chain of “rabid Philippine colonialism.”

Grievances blamed on the central state include: “contagious corruption ... warlord politics ... immoral nightlife intensified by alcoholism, gambling centers and prostitution” to name a few. The rebels despise what their statements deride as the “Filipino psyche — look Asian, think Spanish and act American — which is truly outlandish and a prostituted cultural belief.”

The militants hark back to the days before “Christian colonists” — first Spain, later America now the US-supported Philippine government — tried to subdue their terrain, which was once controlled by Islamic sultans. And they take a very long view of history: The group’s website celebrates the 1521 killing of Portuguese explorer Ferdinand Magellan. Slain by islanders, he was the first European who died trying to Christianize the region.

But behind the spiteful rhetoric, deeper politics are at play.

Notoriously difficult to govern, the Philippines’ southern Mindanao region is home to a bewildering patchwork of large and small Islamic insurgency factions. Some are motivated by banditry and greed, some are motivated by ideology and some are motivated by both. But the MNLF, founded in 1969 by a professor named Nur Misuari, is the poor region’s longest running insurgency group.

It has since been eclipsed in prominence by a faction that split off in the mid-1970s: The Moro Islamic Liberation Front, or MILF, now estimated to control more than 10,000 fighters. After decades of off-and-on government peace talks with various groups, the MILF is leading the latest incarnation of top level, high-stakes negotiations that could finally bring quasi-autonomy and relative peace to the Philippines’ Muslim-majority south.

These peace deals, now in flux, appear to have largely frozen out some of the movement’s founding revolutionaries such as Misuari, who is now 71. His former allies leading the rival MILF faction are now trying to distance themselves from the Misuari loyalists assaulting Zambaonga City.

A statement by the MILF faction states that the “Zamboanga tragedy is not an act of brinksmanship, which great leaders often do, but rather in summary a blunder.” It deems the assault “a wild move that can cause [Misuari] great trouble, perhaps a gradual slipping into oblivion.”

These sentiments are in line with the independence movement’s two long-standing foes: the central Philippine state and the US government, which has expressed support for Philippine security forces as well as Zamboanga civilians “facing their future one day at a time.”

The coastal city and its environs remain under siege. Pauses in fighting — notably one secured by Zamboanga’s police chief during his detention by rebels — have allowed hundreds to escape. But many of those still trapped in embattled neighborhoods, according to Human Rights Watch, are poor residents who lack the money to pay “operators of outrigger boats, which became the only safe way to escape the coastal villages caught up in the fighting.”