CAIRO (AP) — Working in secret, European diplomats drew up the borders that have defined the Middle East’s nations for nearly a century — but now civil war, sectarian bloodshed and leadership failures threaten to rip that map apart.

In the decades since independence, Arab governments have held these constructs together, in part by imposing an autocratic hand, despite the sometimes combustible mix of peoples within their borders. But recent history — particularly the three years of Arab Spring turmoil, has unleashed old allegiances and hatreds that run deep and cross borders. The animosity between Shiites and Sunnis, the rival branches of Islam, may be deepest of all.