The threat is growing. Parisian police have seized 12 suspects in last week’s attacks just a day after authorities thwarted other suspected terrorists in Verviers, Belgium, where a shoot-out killed two militants. And today German authorities arrested two Turkish men with suspected links to ISIS. With European jihadists returning from Iraq and Syria, the continent is on edge. While some attacks are linked to ISIS and others to al Qaida, analysts fear the groups are beginning to compete for gruesome publicity.