According to a recently published report by a scholar at the Marine Corps University, Islamic State (IS) and perhaps even al-Qaeda, having been driven from their territorial strongholds, are likely to take up campaigns of maritime terror. IS successfully carried out an attack on an Egyptian navy frigate, using anti-ship missiles, in the summer of 2015. Michael Rubin explains what could be next:

[T]he Arabs and the Islamic world more broadly have a long and rich maritime legacy, one in which the symbolism-conscious Islamic State can find inspiration. . . .

[The] al-Qaeda military strategist Abu Ubayd al-Qurayshi first sought to integrate maritime operations into a broader jihadist strategy. Al-Qurayshi argued that doing so was especially important to achieve the goal of undermining the U.S. economy, given the importance of trade and the freedom of navigation. . . .

How might al-Qaeda and Islamic State act in the future? In short, they hope to entice the U.S. Navy into narrow waterways off the coast of hostile regions, such as the waters off Yemen and Somalia [as well as] Libya, Egypt, and Syria, and in the Straits of Malacca and the South China Sea. While ships have grown accustomed to treading carefully off the Horn of Africa, Yemen is more difficult to avoid: the Mandeb Strait between Yemen and Djibouti is a chokepoint that shipping transiting the Suez Canal cannot avoid. The same holds true with the Straits of Malacca, especially if extremists succeed in their efforts to gain footholds in Indonesia.

As for the Mediterranean, the development of local gas fields and the rise of Islamic State proxies along its shores mean that it is in play in a way that it has not been since the cold war.