The first wave of Nigerian peacekeepers has received a heroes' welcome from residents of the Liberian capital, Monrovia.
The Nigerians have a tough task ahead of them
At first two battalions are being sent to stop the fighting and provide security so that aid workers can deliver badly needed food, water and medical supplies.
The regional body Ecowas says this force will be beefed up to some 3,000 troops from several West African countries over several weeks.
By 1 October, the United Nations is due to send in a much larger force with contingents from around the world.
When the fighting reached Monrovia in June, Liberians first looked to the United States, which has long historical ties to Liberia and then regional powerhouse Nigeria for salvation.
But they were both wary after their previous experiences of peacekeeping.
"For [Nigeria], it's a question of logistics and then money. For the Americans, I think they are seeing it like a new Mogadishu," says Henri Boshoff, a military analyst at the Institute for Security Studies in Pretoria, South Africa.
The last time the US intervened in an African civil war, 10 years ago, it resulted in humiliation with television viewers around the world seeing dead American troops being dragged through the streets of the Somali capital.
US military planners at the Pentagon are also worried about stretching its forces too thinly around the world, with thousands of troops still in Iraq.
After much debate, President George W Bush ordered three warships to head for the Liberian coast but not to send any troops onto land until a ceasefire was in place.
Nigeria's President Olusegun Obasanjo told the BBC that this was like sending a fire engine to the scene of a fire but only promising to help once the fire was out.
Ecowas first promised to send Nigerian peacekeepers to Liberia on 4 July but the first troops only arrived a month later, during which hundreds of people had been killed by shells and stray bullets.
The delay was partly the legacy of regional powerhouse Nigeria's own past experience of peacekeeping.
Analysts say some 5,000 peacekeepers are needed to end Monrovia's carnage
During the 1980s and 90s, Nigeria led the West African Ecomog peacekeeping force in Liberia and neighbouring Sierra Leone.
Mr Obasanjo said Nigeria had spent some $12bn during two years without any help from the west.
Hundreds of Nigerians were killed and the intervention became unpopular with the Nigerian public.
However, Ecomog did prevent then warlord Charles Taylor from seizing Monrovia, ending the war through negotiation and elections instead.
Mr Taylor has promised to step down but he may be hoping that a West African force will do exactly the same to his opponents.
As in the 1980s and 1990s, the latest Ecowas mission in Liberia includes troops from across West Africa.
The BBC's Liz Blunt, who covered the first intervention, says that each national contingent had its own reputation:
The Ghanaians were everyone's favourite - polite, helpful and well-turned out;
The Sierra Leoneans were well-meaning but hopelessly under-funded. Nigeria had to bale them out with equipment and pay for their troops;
The Guineans were grubby and untidy and the worst of the petty thieves;
The Nigerians were the hard men of the Ecomog force. On checkpoint duty they were considered rude and arrogant, but when there was fighting to be done they were usually the ones who did it, even if they were not too fussy about the finer points of their peace-keeping mandate.
- Towards the end of their time in Liberia, some senior Nigerian officers were accused of getting too cosy with various Liberian leaders and of being involved in business dealings.
The US has promised to pay $10m for the peace force but analysts say this is not nearly enough.
The United Nations will also pick up at least part of the bill, so the soldiers will have the extra motivation of being paid in hard currency..
Monrovia residents have suffered while the peacekeepers delay
But Liberia's problems are still a long way from being solved.
Mr Boshoff estimates that at least 3,000 well equipped and well trained soldiers are needed in Monrovia alone - this will not happen according to the Ecowas plan for at least three weeks.
"It doesn't help you to put in troops that are not competent, that are not robust," he said.
In 2000, hundreds of Zambian troops serving as UN peacekeepers were captured by rebels in neighbouring Sierra Leone, whose civil war has been intertwined with that in Liberia.
The BBC's Liz Blunt says that since its first intervention in Liberia, the Nigerian army has been part of the UN force in neighbouring Sierra Leone, working to common standards with troops from all over the world, and it is from that force that the initial contingent will be drawn.
She says they go back better trained, better equipped and with the benefit of hindsight.
The former head of Ecomog, Nigeria's retired General Victor Malu, says that it will take some 5,000 troops to secure Monrovia and 12,000 for the whole country.
"It's a costly mistake to send just two battalions to Monrovia. You'll be putting the lives of those troops in danger," he told the BBC's Focus on Africa programme.
Now that the peacekeepers have start arriving, Monrovia's residents - who have endured a torrid time during the battle for the capital - are feeling more optimistic.
But ensuring peace in the weeks and months to come promises to be a complex and costly affair.