BAGHDAD - Iraq takes a major step toward reasserting its sovereignty on Tuesday when U.S. combat troops hand urban areas over to its relatively untested police and soldiers.

Will the end of one aspect of the surge strategy -- the ramped-up deployment of U.S. forces in militant strongholds that helped drive al Qaeda and other fighters underground -- lead to a collapse in security?

WILL VIOLENCE SOAR?

It is highly likely that insurgents will increase their attacks following the departure of U.S. combat troops from city centers, both U.S. and Iraqi officials say.

Some militant groups may want to create the impression that they deserve the credit for driving out the occupation forces.

The fact that the partial withdrawal has been dictated by a bilateral security pact agreed last year between the United States and Iraq is immaterial to them.

Some of the insurgents may also think Iraq and its population will be more vulnerable once the Americans pull back to their bases, and that they have a better chance of reigniting widespread sectarian bloodshed through massive bombings.

There have been indications, however, that insurgent and militant groups have lost the capacity to keep up the momentum.

While the past month saw two of the deadliest bombings in more than a year, the overall number of incidents has plunged, and major attacks are followed by weeks of relative calm.

WHAT IS AT STAKE POLITICALLY?

If Iraqi security forces fail to protect the Iraqi people from escalating attacks, Shi'ite Prime Minister Nuri al-Maliki is likely to suffer politically.

He is staking his hopes for a second term after a parliamentary poll next January on his ability to claim credit for a sharp fall in violence over the past 18 months.

Maliki has called the withdrawal a great victory as Iraq tries to shake off stigma of occupation, and he has declared June 30, National Sovereignty Day, a public holiday.

Analysts say he has essentially backed himself into a corner by exalting the occasion -- if violence soars it will be politically unpalatable to call on the U.S. military for help.

The prime minister's stance may also dictate commanders' behavior on the ground. They may be loathe to call on U.S. troops or air cover, no matter how much it is needed, out of fear of being punished by their superiors for apparent weakness.

CAN THE IRAQI SECURITY FORCES PROTECT THE PEOPLE?
The army and national police had to be rebuilt from scratch after U.S. administrators disbanded Saddam Hussein's security apparatus following the 2003 invasion. That left thousands of fighters unemployed and angry, and many joined the insurgency.

Since then, the U.S. military and Iraqi government have spent billions of dollars re-creating, training and equipping a 600,000 strong domestic security force.

Iraqi soldiers at checkpoints now seem a mirror image of the Americans who trained them. U.S. commanders say the police still need more work, but are also better than two years ago.

Where the Iraqi forces fall down is in their vulnerability to threats to their families or bribery.

Corruption has become widespread in Iraq, a major oil producer, and that has led to considerable apprehension among the public over the integrity of the local security forces.

Iraq was a very effective police state under Saddam. Crime and violence, except for that carried out by the state, were ruthlessly stamped out.

WILL THE GOVERNMENT TURN ON SUNNIS AND KURDS?

Once dominant Sunnis and minority ethnic Kurds in the north fear that the U.S. pullback will leave them exposed to the wrath of the Shi'ite-led government in Baghdad.

Maliki's administration has already arrested some leaders of the Sunni-based Sahwa, or Awakening, movement -- U.S.-backed neighborhood guards who once fought alongside al Qaeda.

The guards and some other Sunni groups mistrust Maliki. They believe he is not inclined to give a share of power to Sunnis who often bloodily repressed the Shi'ite majority under Saddam.

Kurds in their semi-autonomous enclave are in a dispute with Baghdad over oil and land, and they fear Maliki's Arab-led government may rein in the independence they have enjoyed, under Western protection, since the first Gulf War.

Once U.S. forces pull back, the risks of a confrontation between Kurdish Peshmerga fighters and the Iraqi army may rise, and Sunni resentment at their political exclusion or a perceived sense of persecution may again fuel the insurgency.

(Editing by Daniel Wallis)

Iraq