Zimbabwe has one of the lowest life expectancies in the world. More than half its population is dependent on food aid and its economy is in tatters.

It hasn't always been like this. Zimbabwe was once viewed as the breadbasket of southern Africa, with some of the best health and education services in the region.

The causes of Zimbabwe's crisis are hotly contested.

Most agree that drought and the HIV/AIDS pandemic are partly to blame. A regional drought in 2005 caused massive crop failures across southern Africa. And over the past two decades, HIV/AIDS has cut down the country's youngest and strongest people, weakening its economic and agricultural infrastructure.

But President Robert Mugabe's political opponents and many in the international community say it is his controversial and often violent land reform programme that has wreaked the most havoc on the country's once strong agricultural base.

Mugabe, in power since independence in 1980, rushed through a series of reforms in 2000, aimed at giving poor black farmers access to good quality land.

The president says the government's seizure of white-owned farms is simply correcting the wrongdoings of the colonial past, but Britain and others accuse him of running the country into the ground.

Southern African states are showing growing impatience with Mugabe. The meltdown has driven millions of Zimbabweans into their countries, straining economies and creating tensions.

Inflation in Zimbabwe has soared over 200 million percent. Unemployment is more than 80 percent.

For the last decade the main opposition in Zimbabwe has been the Movement for Democratic Change. Its leader, Morgan Tsvangirai, has blamed Mugabe for the country's collapse. Mugabe in turn says Tsvangirai is a puppet of the West.

The country's crisis deepened in March 2008 when the two men stood for president. Official results showed Tsvangirai beat Mugabe, but not by enough votes to win outright, forcing a run-off. Mugabe's ZANU-PF party also lost its parliamentary majority.

Violence escalated ahead of the presidential run-off vote in June. The MDC said Mugabe's party deployed security forces, veterans of the independence struggle and youth militia in a campaign of violence and dirty tricks to cripple Tsvangirai's chances of victory.

Scores of MDC supporters were killed and thousands more beaten up, according to the opposition. Police detained Tsvangirai numerous times and arrested opposition legislators, officials, activists, union leaders and journalists.

Tsvangirai pulled out of the race, saying a free and fair poll was impossible and that his supporters would be risking their lives if they voted.

African countries joined Mugabe's Western critics in voicing anger over the bloodshed. The U.N. Security Council also condemned the violence against opposition supporters, although it did not explicitly blame Mugabe's government. Mugabe denied his supporters were responsible for the bloodshed.

Foreign aid agencies were banned from working ahead of the election despite widespread food shortages. The opposition and human rights groups accused the government of using access to food as a weapon to try to sway the vote. The government for its part said the aid agencies were using food to persuade people to vote against Mugabe - an allegation they denied. The ban was lifted in August.

Mugabe, Tsvangirai and the leader of a breakaway MDC faction, Arthur Mutambara, eventually signed a power-sharing deal in September. Talks over the allocation of key ministries were deadlocked for months but a final agreement was reached in January 2009 under strong international pressure.

Tsvangirai was sworn in as prime minister in February 2009. Mugabe remains president with control over security services. But he has relinquished some powers for the first time in nearly three decades of rule - including the health, education and finance ministries.

Zimbabwe's humanitarian crisis has meanwhile been compounded by a cholera epidemic. The outbreak which started at the end of 2008 has killed thousands and left tens of thousands ill. It follows the collapse of the water system, which has forced residents to drink from contaminated wells and streams.

The country's decimated health care services are struggling to cope - Zimbabwe does not have the funds to pay doctors and nurses or buy medicine. Aid agency Oxfam says at least 300,000 people weakened by hunger are in danger from the epidemic.

Mugabe has said in the past that he wants to stay in power until he's sure it will be impossible to reverse his seizures of white-owned farms.

Zimbabwe has a long history of white farmers forcing black farmers off the best agricultural land. This began under British colonial rule and continued when a white minority government declared unilateral independence from Britain in 1965.

Land was an important issue in the ensuing war for independence from white rule. And after a British-brokered peace deal in 1979, the new black government led by Mugabe began a long-term land redistribution programme.

But by 1999, some 11 million hectares (27 million acres) of the best land were still in the hands of about 4,500 white commercial farmers, according to Human Rights Watch.

In 2000, Mugabe introduced new laws that gave the government greater powers to seize land without compensating former owners. The government took over thousands of white-owned commercial farms after backing often violent land invasions led by veterans of the country's 1970s struggle against white rule.

By 2003, about 200,000 black farmers had been given new land, according to the government.

Critics say the process has been poorly managed and underfunded. They say the new owners do not have the money, expertise or state support necessary to farm the land.

According to Refugees International, many of the new settlers were forced to turn to fishing, gold panning and sex work to feed themselves.

Most of the wealthy white farmers who had produced the bulk of Zimbabwe's farm exports have left Zimbabwe, taking with them knowledge and capital.

Zimbabwe's commercial agriculture has plummeted, hitting exports and helping cause the food shortages that have gripped the country since 2001.

The loss of export earnings means Zimbabwe's gross domestic product shrank by almost a third between 2000 and 2004.

Mugabe denies responsibility for the country's out-of-control inflation, saying the economy has been deliberately undermined by his domestic and foreign opponents in retaliation for his land reforms.

The informal sector - economic activity outside the formal, regulated economy - was severely damaged in mid-2005 when the government demolished illegal shantytowns and market stalls. This operation was part of a crackdown on black-market trading, but it left hundreds of thousands homeless and/or without income, according to the United Nations.

Nearly 7 million people were in need of food aid in early 2009, according to the U.N. World Food Programme (WFP). This is a sharp rise from the 4 million who needed help in early 2008.

Soaring inflation makes Zimbabwe's food crisis worse, putting the price of many basic foods beyond a lot of people's means.

The government's food aid programme is run by the Grain Marketing Board which sells maize at subsidised prices. The government says everyone has access to the programme. But opposition leaders and international agencies disagree.

Human Rights Watch says some vulnerable groups are excluded, including farm workers who worked for white farmers, and those living on resettled farmland.

The MDC says its supporters are also barred from the distribution programme.

In the lead-up to elections in 2005 and March 2008, Human Rights Watch said the government had tried to buy votes with food and threatened to cut off aid to people who supported the opposition.

The international response is managed by the WFP and, to a lesser extent, a group of non-governmental organisations called the Consortium for Southern Africa Food Emergency (C-SAFE), which is funded by the U.S. Agency for International Development (USAID).

But the agencies say they have to operate under tight government controls, and find assessing actual needs difficult because the government rarely reveals the size of the country's food stocks.

Zimbabwe officially declared 2007 a drought year but insisted it would not ask for food assistance because it had the capacity to feed its own people.

However, David Coltart, one of Zimbabwe's leading white politicians and a member of parliament for a mainly black constituency, has said the crisis has far outgrown the ability of any single nation to tackle. He has also accused U.N. food and health agencies of a gross dereliction of duty in keeping silent on the issue.

"Zimbabwe is the world's worst humanitarian crisis - but no one is talking about it in public," he told Reuters in September 2007. "It is absolutely catastrophic. The U.N. must act. Not only are people starving to death every day, but the collapse of the economy is starting to destabilise the region."

Zimbabwe has historically had one of the highest HIV/AIDS rates in the world, but in recent years has been hailed for its success in reducing its infection rates.

The estimated HIV prevalence rate among people aged 15-49 was 15.6 percent in 2006-2007, according to a survey cited by UNAIDS, the lead U.N. agency fighting the global pandemic.

This represents a significant drop from almost 34 percent in 2001, and is thought to be partly due to preventative programmes changing sexual behaviour.

It's a success story that has been eagerly promoted by the Zimbabwean government.

Mugabe's government was one of the first to take the pandemic seriously, setting up the National Aids Control Programme in 1987 to lead the national response.

In 1999 Zimbabwe became the first country in the world to introduce a 3 percent levy on taxable income in order to pay for preventative measures and treatment. By the end of 2007, 38 percent of eligible Zimbabweans were receiving anti-retroviral drugs.

However, the government has been criticised by Human Rights Watch for restricting people's access to treatment.

Aid agencies say deaths caused by HIV/AIDS have created hundreds of thousands of orphans.

Millions of Zimbabweans have left to seek a living abroad.

Many of those inside the country have been displaced. Up to 700,000 people were made homeless or lost their jobs in the 2005 crackdown on illegal traders and shantytowns. Another 2.4 million people were affected in some way by the operation, according to the United Nations.

Police bulldozed homes and market stalls in cities across the country in what the government said was an attempt to flush out blackmarket traders and clean up cities.

Mugabe said the operation was part of a plan to build up to 1.2 million new housing units and help small and medium-sized businesses expand.

But months after the operation, most of those who had been displaced were still homeless, living in resettlement camps or struggling to survive without food, safe water or sanitation.

Tens of thousands of former farm workers have also been displaced as a result of land seizures. Some of the workers had been violently evicted by war veterans who seized some of the white-owned farms. About 150,000 labourers were uprooted in 2004 alone, according to Refugees International.

In September 2007, the Internal Displacement Monitoring Centre (IDMC) said in a report that the plight of those displaced by continuing evictions and violent farm seizures was virtually impossible to assess given the lack of access.

"It is clear that sustainable international humanitarian assistance will be impossible unless accompanied by a political process which addresses the broader questions of governance and democracy," the report said.