President Trump inherited several undeclared wars around the world. Will he change U.S. policy? Here's everything you need to know:

Where is the U.S. currently fighting?
President Trump is now overseeing several ongoing combat operations that began during previous administrations. Some 8,400 U.S. troops are still deployed in Afghanistan, the longest-running war in U.S. history, to train and assist Afghan troops in fighting the Taliban. About 5,000 troops are assisting the Iraqi army against ISIS, while another 500 Special Forces fighters are leading the battle against ISIS in Syria. In Yemen, the U.S. has been targeting al Qaeda in the Arab Peninsula and helping Saudi Arabia fight a proxy war against Iranian-backed rebels. In Libya, the Pentagon sent two B-2 bombers to take out suspected ISIS camps just a day before Trump's inauguration. In addition to those combat theaters, the U.S. has bases scattered around the globe, including in South Korea, Turkey, Japan, Djibouti, Saudi Arabia, Germany, and Spain. So far, the Trump administration has given mixed signals about whether it plans to escalate existing conflicts, and about who is setting policy. "Our government continues to be in unbelievable turmoil," Gen. Tony Thomas, head of the military's Special Operations Command, said last week. "I hope they sort it out soon, because we're a nation at war."

What's happening in Yemen?
There's a civil war going on in the small Arab country between the Iran-backed Shiite Houthi rebels and the Saudi Arabia–backed Sunni Yemeni government. The U.S. is providing support for the Saudi-led coalition, mostly in the form of refueling for the Saudi aircraft pounding suspected militants. It has drawn criticism for that support as civilian casualties mount, particularly after Saudi airstrikes that hit a wedding party and a funeral and killed 300 civilians. Direct U.S. involvement in Yemen has mostly taken the form of drone strikes targeting the extremely active al Qaeda affiliate based there, such as the 2011 strike that killed American-born cleric Anwar al-Awlaki. After President Trump's ground strike on an al Qaeda commander there last month degenerated into a protracted firefight — killing a Navy SEAL and 23 civilians as well as a dozen militants — Yemen asked for a "reassessment" of U.S. ground raids. The Trump administration insists that operation was "a success," but has not indicated whether it will alter existing U.S. policy toward Yemen's civil war.

What about ISIS?
The U.S. is taking a leading role in the fight against what's left of the Islamic State in Syria, Iraq, and part of Libya. Last year, the U.S. bombed ISIS strongholds in Libya, including the key port of Sirte, for weeks. In Iraq, U.S. troops have been embedded with the Iraqi army as it tries to retake Mosul from ISIS. But Iraqi lawmakers say Trump has endangered that relationship. (See below.) The president is reportedly considering deploying ground troops to Syria to speed up the effort to destroy ISIS, and has also said he'd like to coordinate military efforts with Russia. Analysts say that Russia is truly not fighting ISIS in Syria, but instead has deployed most of its troops, airpower, and equipment to shore up President Bashar al-Assad in his civil war with various militias, including Kurdish militias allied with the U.S.

What's the status of Afghanistan?
The 8,400 U.S. troops in Afghanistan maintain bases to support the Afghan government and assist the Afghans in fighting a continuing Taliban insurgency. The Pentagon has asked for more troops to help train Afghan forces, and Trump reportedly told Afghan President Ashraf Ghani in a phone call that he was considering a troop surge. The U.S. commander in Afghanistan, Gen. John W. Nicholson, said this month that the Taliban currently controls more Afghan territory than at any time since 2001. He said the fight there is "in a stalemate," because Taliban fighters can easily find sanctuary in neighboring Pakistan and mount attacks from bases there.

What about North Korea?
The Stalinist dictatorship, which has been building an arsenal of nuclear bombs, just tested a new intermediate-range missile. The missile shows technical elements that indicate North Korea is closer to creating an intercontinental ballistic missile that could reach the U.S. mainland with a nuclear warhead. In January, Trump tweeted that an operational North Korean ICBM "won't happen!" but he made no direct statement about the February test. However, Trump has said in the past that he would pressure China to rein in its rogue client state. "China has control, absolute control, over North Korea," he said. "And they should make that problem disappear." China, however, has always been reluctant to intervene in North Korea, and already has had much friction with the Trump administration over trade, Taiwan, and Beijing's territorial claim over the South China Sea. China, for its part, says Trump should deal directly with Pyongyang. "We believe," said Foreign Ministry spokesman Geng Shuang, "that dialogue and consultation offer the way out."

The impact of the travel ban on allies
President Trump's executive order temporarily banning all refugees and all visitors from seven majority-Muslim countries has been halted by the U.S. courts, but it has already had an effect on U.S. troops abroad. Five of the seven countries covered under the order are places where the U.S. is engaged in military operations: Iraq, Syria, Yemen, Libya, and Somalia. That means some of the people excluded are locals who have been helping the U.S. at great personal risk — particularly in Iraq. "This has caused massive disappointment in the hearts of every Iraqi who is fighting radicalism," an Iraqi general told Fox News. Iraqi militias, including the Hezbollah Brigades, have threatened an "earthshaking response" against U.S. troops in Iraq. Trump has also alienated Iraqis by repeating his belief that the U.S. should "take Iraq's oil" — which would be illegal under international law. "There is nothing Trump could have said that would be more corrosive to our interests in the Middle East," says Ryan Crocker, former U.S. ambassador to Baghdad. "It plays to the myth that we were in Iraq to take their oil." Once ISIS is defeated, Crocker said, fears that U.S. troops will steal Iraq's oil could lead Iraqis to attack U.S. troops.