Robert Fisk: In Tripoli, posters of martyrs in the market place say it all – and more are on the way

The Long View: Lebanese troops lounge in the jeep opposite Ali's office, just as they stop dodgy-looking motorists

The posters, as usual, say it all. There are a new clutch of martyrs above the Tripoli market, Sunni Muslims all – Khodr al-Masri's grim face is that of a man who seems to have guessed his fate earlier this month – while round the corner, at the edge of Syria Street, President Bashar al-Assad beams down upon me. "Syria, Assad," it says. "God is protecting Syria." I drop into the little office of the Arab Democratic Party, black plastic, fake-leather sofa, black plastic armchairs, black laminated desk, all very fetching, and I ask Ali Fhoda – at 29, the youngest member of the party – if he's met Bashar. "I wish," he says. Time running out, I say to myself.

Ali is, of course, an Alawite – the Shia sect of his hero Bashar – and here on the little hill of Jebel Mohsen, one of the slummiest areas of Tripoli, most of the Lebanese city's 60,000 Alawite poor live. If you believe the Sunni lot, it's a bastion of Syrian secret policemen and Iranian Revolutionary Guards pouring gunfire into the Sunni district of Bab el-Tabaneh in a Bashar-oriented attempt to spread Syria's civil war into Lebanon. If you believe Ali – and I'll come to that in a moment – it's a lone and poorly armed suburb, surrounded and under constant mortar and bazooka fire from the Sunnis and their rebel allies in Syria, along with Saudi and Qatari "jihadis" who are trying to drive the Alawite lot out of Tripoli.

Lebanese troops lounge in the jeep opposite Ali's office, just as they stop dodgy-looking motorists, which they've been doing since 15 people (12 Sunnis, three Alawites) were killed nine days ago. Across at the interface where the ancient Chateau de Saint Gilles forms the front line, the army has also installed itself, Lebanese troops occupying a Christian Crusader castle to stop two bunches of Muslims from shooting each other.

Ali reads seven hours a day – which I believe – and says there is simply no way out of Jebel Mohsen, which I do not believe. "There are always sniping operations against us after battles," he says. "We are surrounded on all sides. If the Lebanese army didn't bring us flour, we wouldn't survive."

But then a few minutes later – after quoting Kissinger and Bashar's father Hafez al-Assad at considerable length – he trips up and tells me he went to Beirut a few days ago. How? "There's a secret route and I went with security." Aha, so that's how the weapons get into Jebel Mohsen, I say, as Ali denies any such notion.

Ali believes that his people are not sectarian but that the "terrorist gangs" on the other side of town – he uses Bashar's exact words for his enemies – are trying to undermine Syria. "Kissinger said that Syria could not be occupied, but it could be fragmented," he says. "There will be an eventual settlement in Syria. The idiots cannot take Syria to bits like they took Libya and Egypt to bits."

This is a pretty exclusive view of history, but Ali takes it seriously; his brother bled to death in Tripoli's street battles four years ago. They couldn't get him to a hospital.

So across town to the delightful apartment of my favourite Lebanese doctor, Mustafa Aloushe, half-Alawite himself but very firmly not in the Assad camp. He's an official of the Future Party of Saad Hariri – ex-Prime Minister and son of assassinated ex-leader Rafiq Hariri – and has performed five medical operations when he comes in for lunch, describing them with the enthusiasm of a real surgeon. Lunch is great. And he's quite on the record about everything. Yes, he believes Najib Mikati, the cheerful Sunni Prime Minister of Lebanon, funds one group of Sunni gunmen and Hezbollah is sending weapons to another Sunni group.

Najib, whom I chatted to monthly when he ran my local phone company, is a millionaire but denies any militia payments. I should add that Mikati is from Tripoli, along with General Rifi, one of the most powerful (and anti-Syrian) security men in Lebanon, and so too is the admiral of the Lebanese navy.

So get this. If Mustafa spoke the truth, Hezbollah – Syria's Shia ally in Lebanon – is arming Syria's Sunni opponents in Tripoli, with financial help from a Prime Minister who heads a pro-Hezbollah government in Beirut, while Syria's supporters are shooting back with training from Syrian intelligence agencies. Even for Lebanon, this seems too much. Ali Fhoda's line, of course, includes Assad's claim that enemies use Tripoli to funnel weapons to "terrorists" in northern Syria.

This bit, I do believe – because the army found a truckload of weapons en route to Syria which had been shipped into Lebanon on a boat registered in Sierra Leone. Mustafa thinks the fighting will continue "but it's not a war". Three hours later I flick on the car radio. A man in Jebel Mohsen has been shot dead by a sniper, his wife wounded. Another martyr's poster is on the way.