After a nearly month-long bombing campaign in Yemen by a Saudi-led coalition of 10 Arab countries, the Saudi government announced Tuesday that it would halt its attacks. It is unclear if the decision will lead to peace talks between the antagonists in Yemen, the region’s poorest country, where the mounting crisis has drawn regional powers Egypt, Iran and Saudi Arabia deeper into a violent struggle for influence.

Here is a look at the crucial divisions and the parties to the conflict.

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    Source: American Enterprise Institute's Critical Threats Project Credit By The New York Times
    Geography of Chaos in Yemen

    Yemen, historically divided between Shiites, who live mostly in the northeast, and the majority Sunni population who live in the southeast, is important to regional players and the United States.

    The Houthis are a Shiite insurgent group that fought the government of President Ali Abdullah Saleh intermittently from 2004 until he agreed to step down in 2011, in the wake of protests inspired by the Arab Spring.

    Less than four years later, the Houthis are now collaborating with security forces still loyal to Mr. Saleh, a reflection of the shifting alliances at work in Yemen.

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    Houthi militiamen stood guard on a wall surrounding the old city of Sana in January. Credit Yahya Arhab/European Pressphoto Agency
    Who Are the Houthis?

    The Houthis are a Shiite sect from Saada Province. With support from Iran, militants took control of the capital, Sana, and in January forced the resignation of Mr. Saleh's successor, President Abdu Rabbu Mansour Hadi.

    The Saudi-led airstrikes crippled Yemen’s air force, but there has been no indication that the Houthis or their allies have retreated from Sana, or areas they occupy farther south, including parts of Aden.
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    The site of an airstrike near the Sana airport on Thursday. Saudi Arabia and nine other countries began military operations in Yemen to counter the Houthis. Credit Khaled Abdullah/Reuters
    Saudi Arabia's Support for President Hadi

    The leaders of Saudi Arabia, which shares a border with Yemen, are especially worried about the Houthis because they are backed by Iran, a regional rival.

    The Saudis led a month-long military assault against the Houthis and in support of President Hadi.

    Mr. Hadi escaped to the port city of Aden, south of the capital, where he and forces loyal to him took refuge, and is now in Saudi Arabia.

    The Saudis have said military action was necessary to restore Yemen’s government. But the Saudi intervention raises the possibility of a proxy war in Yemen and a wider regional conflict.

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    President Abdel Fattah el-Sisi of Egypt at the Arab League meeting in Sharm el-Sheikh, Egypt, on March 29. Credit Khaled Elfiqi/European Pressphoto Agency
    Egypt Aims to Counter Islamist Extremists

    A day after the Saudi-led airstrikes began, another Arab ally came to the support of Mr. Hadi. President Abdel Fattah el-Sisi of Egypt said in a statement that the country’s navy and air force would join the campaign. The Egyptian Army, the largest in the Arab world, was ready to send ground troops “if necessary,” Mr. Sisi said.

    Antagonists on either side of the Yemeni conflict are braced for a prolonged battle as the country — like Iraq, Libya and Syria — is consumed by a civil conflict, regional proxy war and the expansion of extremist groups.

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    The American born cleric Anwar al-Awlaki, who was a leader of Al Qaeda in the Arabian Peninsula, in 2010. Credit Agence France-Presse — Getty Images
    Al Qaeda's Branch in Yemen

    Militants of Al Qaeda in the Arabian Peninsula attacked government buildings in Aden on April 2, breaking out of prison a top Al Qaeda leader and hundreds of others.

    It was the latest example of how, as the situation in Yemen has degenerated, Al Qaeda's affiliate there has grown more assertive.

    After the Houthis began establishing their control of increasingly wider swaths of the country last year, and promised political change, their supporters were hopeful stability could be restored.

    Instead, the Sunni militants of Al Qaeda, who regard the Houthis as heretics because they are members of the minority Zaydi sect, an offshoot of Shiite Islam, have retaliated with growing ferocity.

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    Yemenis gathered around a car after it was targeted by a drone strike that killed three Qaeda militants in Marib, Yemen. Credit Agence France-Presse — Getty Images
    U.S. Interests in Yemen

    The United States, which has backed Saudi Arabia in the Yemen conflict, moved to deploy a strengthened armada of warships off Yemen’s coast, in what was seen as a warning to the Iranians not to rearm the Houthis.

    Until the growing chaos forced the evacuation of 125 United States Special Operations advisers last month, Yemen served as a partner in American counterterrorism operations, mainly against Al Qaeda’s affiliate in Yemen. Without American eyes and ears on the ground, efforts to thwart Al Qaeda will be more difficult.

    American officials fear that the emerging security vacuum could attract even more jihadists to Yemen. On March 20, a group calling itself an affiliate of the Islamic State claimed responsibility for bombing Shiite mosques, increasing fears that it will try to ignite the sectarian tensions already roiling Yemen.

Correction: March 26, 2015

An earlier version of this article misstated the year that Ali Abdullah Saleh stepped down as president. It was 2012, not 2011; he agreed to step down in 2011.