Shortly after being made a count of Empire, Vandermaesen's 5th Division fought in the Battle of San Marcial. In command of 10,000 men of the rearguard, he found that the Bidassoa River had risen too high for his soldiers to cross at the fords. The only bridge in the area was guarded by a company of British riflemen defending loopholed buildings while the gunpowder of the French was soaked by a heavy rain. While supervising the storming of the bridge at Vera in the early hours of September 1, 1813, Vandermaesen was killed by a gunshot in the side. Though the French suffered heavy casualties, the rest of the column escaped the trap due largely to a British error. His son was granted the title of baron in 1814.