European countries have thousands of troops in Afghanistan, Iraq and elsewhere in the Middle East, where they mainly operate alongside much larger U.S. deployments. Iran, meanwhile, is allied with powerful armed groups in Iraq, Syria, Lebanon and Yemen. That’s why the words of Iran’s president that European troops in the Middle East “could be in danger” if their nations join the U.S. maximum pressure campaign against the Islamic Republic are resonating far beyond the region. President Hassan Rouhani’s warning comes against the backdrop of a major escalation in tensions between Tehran and Washington this month.