British Prime Minister Gordon Brown has vowed a renewed effort to defeat the Taliban insurgency during a visit to Afghanistan and has called the next few months as critical. He was speaking on arrival at Kandahar airfield today on a previously unannounced visit to Afghanistan. The British leader's visit to Afghanistan comes two weeks after ordering 500 extra British troops into the war alongside a surge of 30,000 American forces as part of a sweeping new US strategy to turn around the eight-year war . Mr. Brown held over an hour of talks with Afghan President Hamid Karzai at a military base in Kandahar, the southern province where the Taliban was born and one of the deadliest battlefields for NATO and US troops since the 2001 US-led invasion.