Mattis emphasized the importance of the U.S.-Saudi relationship amid the destructive civil war in neighboring Yemen.
The defense-friendly bill gives the Pentagon a top line budget of $700 billion.
Researchers and engineers at RAND explain what a hypersonic weapon is, which countries are developing them, and how the U.S. could look to defend against them.
Gen. John Hyten, the commander of U.S. Strategic Command, would hold off on launching nukes.
The Saudi delegation is slated to meet with defense industry giants Lockheed Martin and Boeing.
America's top nuclear commander says the U.S. doesn't have a defense system in place to counter hypersonic weapons.
The defensive drills, which have been carried out regularly for nearly 40 years, showcase a spectrum of air, land and sea operations.
The call between Trump and Putin comes as the special counsel's investigation into Russian meddling in the 2016 U.S. election intensifies.
The discussions between the Saudi crown prince and Trump are expected to play a "critical role" in the president's next steps regarding the 2015 nuclear agreement, a senior administration official said.
Here's a look at how many nuclear weapons exist and which countries stockpile them.