The security architecture of the Caspian Sea, the largest enclosed inland body of water in the world, may soon change. Of all the states that border the sea — Russia, Iran, Azerbaijan, Turkmenistan and Kazakhstan — Russia has the strongest navy, and military activity in Caspian waters tends to reflect its strength. But that may no longer be the case. Azerbaijan and Kazakhstan appear determined to develop their own naval capabilities, ones that would function independently of Russia. On Nov. 4, they signed a bilateral defense cooperation agreement that will take effect in 2016. The agreement emphasizes joint naval exercises and invites officials in Azerbaijan to attend KADEX, an arms exhibition held in Kazakhstan. Their interests in the Caspian are well founded: Its waters are rife with hydrocarbons resources.