Boko Haram is one of the most effective and successful guerrilla groups anywhere.
Nowhere in the north-east of Nigeria is safe nowadays from it. It has even carried out attacks in distant cities like Kaduna, Kano and the capital, Abuja.
What shocked me was that Boko Haram could launch a major attack on a smallish town like Gamburo, close to the border with Cameroon, and kill 375 people - and yet this would scarcely be reported in the rest of Nigeria, let alone the outside world.
It happened eight days ago. My television team and I went there with the local governor, Kashim Shattima. Mr Shattima is a brave and conscientious man, but his security team made him wait for an entire week before allowing him to go there.
And when he went, it was in a convoy of 40 vehicles, most of them full of armed men.
At first I thought it was absurd. But the further we drove, the more I realised how necessary it was. Even the outskirts of his capital, Maiduguri, have regularly been attacked. Beyond the ceremonial arch on the edge of town, Boko Haram has more power than he does.
'Cold and methodical'
All along the road as we drove we saw abandoned villages whose people had left for the relative security of Maiduguri.
The road was empty, because it is so dangerous to drive along it. Afterwards I spoke to a man in Maiduguri whose car broke down on the road. When he got out he saw a pool of blood and several empty shell-cases on the road. Boko Haram had just staged one of its regular roadside attacks there.
The situation in Gamburo itself was quite extraordinary. Over the years I have seen dozens of towns which have been attacked by guerrillas, from Bosnia to Angola and from Iraq to Peru. But I have never seen damage on this scale.
Boko Haram attacked it with a fury that is fortunately rare. It was as though they wanted to wipe it off the face of the earth. They arrived in extraordinary force - there were 400 of them, according to one man who watched the attack from hiding - and set about killing people and destroying cars and buildings coldly and methodically.
The soldiers in the town had previously been ordered somewhere else, and the police, who were its sole defenders, ran away. Only the members of the local home guard, armed with machetes and bows and arrows, stayed and fought.
As we wandered round the wrecked buildings with the governor, people told us they felt utterly deserted by the federal government in Abuja. And although the governor had come to offer them help and money, they screamed him down even as he was trying to tell them about it.
Soon the crowd was thoroughly stirred up, and if someone had thrown a stone or hit him I think they would have killed him. In spite of our bodyguards and our 40 vehicles, we had to get out of town fast.
None of this rage was really directed at the governor. In fact, several people told me how they respected him for going there. It was aimed at a government in Abuja which seemed to have decided that this part of Nigeria didn't matter.
"They have left us to our fate," a shopkeeper said to me.
These people feel completely abandoned. And they find it hard to understand why a world which cares deeply about the fate of 270 missing schoolgirls seems to care so little about the destruction of an entire town.