By Roger Hardy
BBC Middle East analyst
The more immediate causes of Lebanon's current - and apparently unending - political crisis go back to the war between Israel and the Lebanese Shia movement Hezbollah in the summer of 2006.
Rival factions are struggling for control in an outdated system
After standing up to the powerful Israeli military for a full month, Hezbollah declared it had achieved a "divine victory".
Its leader, Hassan Nasrallah, was the new hero of the Arab street.
The movement was determined to turn its success to political advantage within Lebanon itself.
It stepped up the pressure on the government of Fuad Siniora, which it attacked as illegitimate and a tool of western interests in Lebanon.
Shia ministers withdrew from the government, Hezbollah brought its supporters out onto the streets - and the country was plunged into prolonged political paralysis.
State without a head
As ever in Lebanon, the confrontation had an external as well as an internal dimension.
The United States and its key Arab allies, Saudi Arabia and Egypt, supported Prime Minister Siniora. Iran and Syria backed the Hezbollah-led opposition.
Symptomatic of the depth of the political malaise is the fact that the country has been without a president since November 2007.
After months of haggling, the political factions can agree on who the next president should be - but not on the composition of a new government.
So the deadlock persists, with the constant danger of violent escalation.
By general consent, it is the country's worst crisis since the civil war of 1975-90. But to understand the underlying causes, one must go further back in time.
Ever since its creation in the aftermath of the First World War, Lebanon has had a fundamental problem of identity.
Hezbollah wants political influence in proportion to its military success
Is it an Arab or a non-Arab state? Should it look East or West? How should its mosaic of Muslim and Christian communities - 18 in all -share power?
The political elite attempted to solve the power-sharing problem in the National Pact of 1943.
The president would be a Maronite Christian, the prime minister a Sunni Muslim, the speaker of parliament a Shia Muslim. Other posts would be divided up along confessional lines.
The formula is still followed, but over time the consensus that underpinned it has eroded.
The Christians, originally a majority, became a minority.
The dominant Maronite-Sunni alliance came under challenge from the historically marginalised Shia - the largest minority in a nation of minorities.
Disastrous civil war
In 1975, internal and external tensions, aggravated by the country's proximity to Israel and the Palestinian problem, exploded in conflict.
What is under way is not just a battle for control of one small country, but a wider regional battle between pro-Western and anti-Western forces
A disastrous civil war dragged on for 15 years. Lebanon emerged physically shattered and under control of its two more powerful neighbours.
Israel occupied a buffer zone in the south, until a Hezbollah guerrilla campaign succeeded in driving it out in 2000.
Beirut and much of the rest of the country was under the thumb of Syria, until the wave of anti-Syrian protests after the assassination of former PM Rafik Hariri.
But if the domestic factions have never managed to resolve the Lebanese conundrum, no external player has managed to do so either.
Iran, the US and the old colonial power France - as well as Syria and Israel - all are involved, but their periodic interventions have not brought a definitive solution.
Indeed some would argue they have made things worse, by using Lebanese soil to fight their proxy wars.
It is because of this complex interplay of the internal and the external that Lebanon matters.
Instability there feeds, and is fed by, regional instability.
In the current context, what is under way is not just a battle for control of one small country, but a wider regional battle between pro-Western and anti-Western forces.
Put starkly, Iran and Syria would regard the containment of Hezbollah as an unacceptable victory for the US and its allies.
Victory for Hezbollah, on the other hand, would be seen in Washington, Paris, Riyadh and Cairo as handing over Lebanon to Iran.
While the central issue is power and the balance of power, there is a dangerous sectarian undercurrent.
The politics are complicated. The stakes are high.