Months of relative calm in the long-simmering trade war between the U.S. and China may be coming to an end. A spate of moves between the two nations this week has thrust trade hostilities back in the global spotlight, roiled stock markets and raised alarms of what might come next. China announced strict new limits on exports of rare earth minerals crucial to high-tech products. The U.S., in turn, has threatened an additional 100% tax on Chinese imports and export controls on American software. Both sides also hit one another’s ships with new port fees. Experts say it is unclear if it all means a rapid escalation is inevitable or if the threats could pave the way for an agreement.