There's no doubt the departure of Pakistan's president Pervez Musharraf was overdue. Facing almost certain impeachment from his political opponents, Musharraf's nine-year tenure had been marked by chronic violence, deep political unrest and painfully feeble attempts to regain his country from the grip of terrorist factions.

Indeed, since 2001, the United States has pumped more than $10 billion in aid into Pakistan. Yet Musharraf allowed the Taliban and al-Qaida to control his country's tribal pockets and take root along the Afghanistan border. And Pakistan's people remain among the poorest in the world.

But Musharraf's departure also poses some steep challenges.

First, finding allies among the fractious government parties will be difficult; efforts to fight militant forces are widely unpopular and are seen as largely an American problem forced upon the country.

Building trust and political bridges will take time — and time is clearly not on our side.

The tenuous control over Pakistan's nuclear arsenal, which is estimated at 50 to 100 weapons, is among the greatest concern, U.S. officials say. There are well-founded worries the Taliban and al-Qaida will aggressively seek support within a new regime.

Pakistan is an important military theater: This nation of 165 million is bordered by Iran, Afghanistan, India and China. Urgent work must begin to secure stability in the region through careful diplomacy and the right amount of pressure.