Marines deployed to the Middle East in support of Operation Epic Fury train their marksmanship skills aboard the amphibious assault ship USS Tripoli. US Central Command Public Affairs Marines are training for a future where they're likely to be constantly watched by adversaries. Top infantry commanders say deployments and new demands are stretching the force thin. Leaders say adapting to new ways of war amid constant deployments is beginning to strain readiness. The US Marines believe future wars will require fundamentally new skills and ways of fighting, but commanders worry that current demands are consuming precious time needed to prepare for tomorrow's battlefields , likely to punish even small shortcomings. Getting ready for potential future fights defined by drones , constant surveillance, and electronic vulnerability requires time, predictability, and repetition — all increasingly hard to sustain.…