Q. What regional partners are crucial to the effort, and what are the obstacles to their participation?

A. Mr. Obama is marshaling a coalition that includes Britain, France, Germany, Italy, Poland, Denmark, Canada, Australia, Jordan, Turkey, Saudi Arabia, and the United Arab Emirates. Turkey’s involvement is critical because it can provide military bases and close off transit points for foreign fighters, while Saudi Arabia is a key source of funding for Syrian rebels. But Turkey fears jeopardizing 49 Turkish hostages held by ISIS in Iraq, while Saudi Arabia worries about a backlash from extremists in its own Sunni population.

Q. What options do the United States and its partners have to target ISIS, beyond airstrikes?

A. The campaign Mr. Obama is set to announce will include military, diplomatic and even ideological components. It will aim to reinvigorate Syria’s moderate opposition to turn it into a fighting force capable of seizing and holding ISIS territory, after airstrikes by the United States and its partners. In Iraq, the goal is to win over disaffected Sunni tribal leaders to fight ISIS — a strategy that echoes the Sunni Awakening during the Iraq war, which turned insurgents into allies. Crucial to that effort is the new government in Iraq and its success in reaching out to Sunnis. The administration also hopes to counter the narrative that ISIS has propagated, a difficult task given its deft use of social media and the allure of jihadi messages in the Arab world.

Q. Does the president plan to seek congressional authorization for military action, and if not, why not?