Defense Secretary Robert Gates has decided to send an additional 1,400 Marine combat forces to Afghanistan to bolster U.S. troops ahead of a possible spring offensive by Taliban fighters returning from hideouts in Pakistan. The Marines will be deployed to the south of the country, around Kandahar, where the U.S. has been amassing forces. The new troops will help the military shore up security in the troubled southern region. They will protect U.S. gains made over the past few months before the Obama administration-mandated reduction of troop levels begins in July. Commanders have been under pressure to show security improvements this year lest the administration decide its strategy has failed and accelerate the troop pullout. The new Marines could arrive by mid-January, and as many as 3,000 fresh troops may eventually be deployed.