A dizzying series of military moves in the Middle East and other nations in the vicinity over the past few days are ramping up tensions in the region, and between the U.S. and Russia. The key incidents, and why they matter:

Syria

• The U.S. shot down a Syrian fighter jet Sunday after it bombed U.S.-backed forces. This is the first time the U.S. has engaged in air-to-air combat with Syrian forces since the start of the six-year civil war, signaling an escalation.
• Russia warned the U.S. after that incident that it would target U.S. aircraft west of the Euphrates. Monday a Russian fighter jet came within five feet of a U.S. reconnaissance aircraft in the Baltic Sea in an unsafe maneuver. For weeks Russia has been encouraging pro-regime forces and the U.S. both to not attack one another, so this marks an increased willingness from Russia to publicly back the regime over the coalition.
• The U.S. shot down a pro-Syrian drone Monday even after the Russian warnings, marking the third such downing this month. The drone was Iranian-made.
• Iran launched missiles against ISIS Syria's Deir al-Zour region in retaliation for an attack on Tehran last week. Iran said it would launch future strikes against ISIS. Iran hasn't launched missiles into another country for three decades, per CNN. Plus, Deir al-Zour is where the fight in Syria will likely come to a head after Raqqa falls (more on that here).
• Russia said Friday it may have killed ISIS leader Abu Bakr al-Baghdadi last month, which the White House could not corroborate. Iraqi leaders were also skeptical of the announcement.

Saudi Arabia

• The Saudi Navy detained three Iranian Revolutionary Guard Corps members over the weekend, claiming their vessel had explosives intended to carry out a terrorist act in Saudi territorial waters. Tensions between Saudi Arabia and Iran are at a high since Saudi Arabia cut ties with Qatar over its support for Iran.

Iran

• An Iranian navy boat made an unsafe maneuver against a U.S. flotilla in the Straight of Hormuz last week and Sunday Iran and China carried out joint naval exercises near the Straight of Hormuz.

Qatar

• The U.S. Navy carried out military drills with Qatar over the weekend, amid the tensions between Qatar and its neighbors. (Turkey also participated in military drills in Qatar, although reportedly the drills were planned in advance of the Qatar diplomatic crisis.)

Afghanistan

• Last week an insider in Afghan forces opened fire on foreign troops in Afghanistan, marking the second such attack in which the Taliban may have infiltrated Afghan forces. This adds a security concern ahead of the upcoming deployment of 4,000 U.S. troops to Afghanistan.