The decapitated bodies of the soldiers lined a major boulevard, accompanied by a sign: "For every one of mine that you kill, I will kill 10." A bag of their heads, some still gagged with tape, was found nearby. The discovery in Chilpancingo, an hour north of the resort of Acapulco in southern Mexico, marked the most gruesome attack yet against the Mexican army in its half-century battle against drug gangs. The government honored the dead Monday in a high-profile ceremony aimed at reassuring the nation that it won't surrender, despite escalating violence that has killed 5,300 people this year and the betrayal of more than a dozen top law enforcement officials accused of accepting money to protect cartels. The beheadings also came as Mexico prepares to use $400 million in US aid to fortify its war on traffickers.