Although the Yemeni military is claiming that it is winning the battle against militants who have occupied territory in Southern Yemen the actual situation seems more complex. The military does seem to have regained some territory including a strategic town of Lawdar.
However other areas are still under control of militants of Ansar al-Sharia and AQAP (Al Qaeda in the Arabian Peninsula). The press and official pronouncements tend to link groups together perhaps to convince the U.S. that these are all Al Qaeda militants or Al Qaeda linked. It works.
The U.S. has been involved in several air strikes, including one that is said to have killed some militant leaders. Often strikes that are said to be by the governmet are no doubt by the U.S. Wikileaks cables revealed that at least the former government took credit for U.S. atttacks so as to downplay U.S. involvement. Probably the present government is doing the same. There are U.S. Special Forces units operating in Yemen as well.
The struggle against militants has been costly as the most recent attack killed at least 32 soldiers. Some time ago the rebels raided a base outside of Zinjibar killing 185 soldiers and captured many others. Those captured were later released. See this article. The U.S. is strongly backing President Hadi as he has made a strong commitment to defeating Islamic. However Hadi faces opposition from within his government and two separatist movements as well as the Islamic militants who oppose his government. For more see this article.