The China-India-Pakistan triangle has never been short on danger, but Islamabad’s new defensive alliance has added another variable to an already volatile situation. Last week, Pakistan, Turkey and Saudi Arabia signed a pact in Mecca in which they agreed to treat an armed attack on one as an attack on all. The three governments have described it as defensive and not directed at any particular state. Analysts said its main significance for India lay less in whether it would be invoked, but in how...

The grand security bargain between the United States and Gulf countries is widely perceived to be fraying, creating what analysts see as an opening for Beijing to expand its presence in the region. For decades, Saudi Arabia and other Gulf states relied on Washington’s defensive shield, while it in turn relied on them for access, energy and influence. Riyadh’s decision to sign a mutual defence agreement with Turkey and Pakistan is the clearest sign yet of that shift. Signed this week in Mecca,...