KABUL (Reuters) - NATO's expansion into southern Afghanistan will target drug warlords who are the root cause of growing violence, the force's commander said on Saturday. NATO will embark on the biggest mission in its history on Monday when it takes over security from the U.S.-led coalition in six southern provinces, extending its authority to almost all of the country. British Lieutenant-General David Richards said he hoped to see improvements in the south within three to six months, which would allow the 26-nation alliance to proceed with the final phase of its deployment into the east by the end of...