Hollywood action hero Chuck Norris has warned Texans to be vigilant during a massive US military training exercise that he fears could turn into a full-blown occupation of the Lone Star state. The US military has denied a widespread conspiracy theory that it is planning to impose martial law in Texas using secret tunnels dug under Walmart stores.Operation Jade Helm 15 will see 1200 US commandos testing out their skills in Texas and several other southwestern states, sometimes dressing in civilian clothes and moving in unmarked vehicles as part of their covert warfare training.Norris, who starred in The Delta Force,wrote online: "The US government says 'It's a training exercise', but I'm not sure the term 'just' has any reference to reality when the government uses it.' [Who is] pulling the strings at the top of Jade Helm 15 back in Washington?"A spokesman for the US Special Operations Command addressed a community meeting in Texas in late April where he received a frosty reception from residents who peppered him with questions about Operation Jade Helm.One man said he "didn't believe a word the colonel was saying". Greg Abbott, the governor of Texas, has ordered Texas national guard troops to "monitor" the US forces taking part in Operation Jade Helm."Your letter pandering to idiots has left me livid," one former Republican politician wrote to Abbott...