Experts say the new threats in the Bab-al-Mandab is putting the Navy in a situation familiar to the Army and Marine Corps in recent years: operating under the constant threat of attack. "It makes the Navy very concerned, and it reminds them that ships are vulnerable," said Bryan Clark a retired commander and analyst with the Center for Strategic and Budgetary Assessments. "They are easy to identify and they operate in close proximity to threats. "It puts a premium on being able to defend yourself on very short notice. The Navy has invested money in self-defense for years, however, and regularly trains to meet both small boats and missiles. The rising threat of attack in the Bab-al-Mandab is going to test whether those investments are going to pay off, Clark said.