In the eyes of Mike Pompeo, the day was shaping up to be one of his most commanding displays of diplomacy since becoming secretary of state. Months of planning had finally yielded a meeting among reluctant European officials, Arab leaders and the Israeli prime minister to strategize over confronting Iran.

In the first generation of the online revolution, the question would have seemed absurd. In his new book The Perfect Weapon: War, Sabotage and Fear in the Cyber Age, Belfer Center Senior Fellow David Sanger addresses why that question has become less outlandish.

More than 30 high-tech companies, led by Microsoft and Facebook, announced a set of principles on Tuesday that included a declaration that they would not help any government — including that of the United States — mount cyberattacks against “innocent civilians and enterprises from anywhere,” reflecting Silicon Valley’s effort to separate itself from government cyberwarfare.

President Trump’s threat to rip up the Iran nuclear deal has touched off an urgent scramble in European capitals to preserve the agreement — not by rewriting it, but by creating a successor deal intended to halt Iran’s ballistic missile program and make permanent the restrictions on its ability to produce nuclear fuel.

Although cyber weapons can usually be employed in a far less lethal manner than guided missiles shot from a drone, they have been deployed less frequently and under rules of engagement that are far less clear, at least to the public.

Iran’s top nuclear negotiator was heading back to Tehran on Sunday to consult with his nation’s leadership, as negotiators remained divided over how to limit and monitor Tehran’s nuclear program and even on how to interpret the preliminary agreement they reached two months ago.

Five former members of President Obama’s inner circle of Iran advisers have written an open letter expressing concern that a pending accord to stem Iran’s nuclear program “may fall short of meeting the administration’s own standard of a ‘good’ agreement” and laying out a series of minimum requirements that Iran must agree to in coming days for them to support a final deal.