I don't think you realize what a "battlefield" is now-a-days. It's typically 500m between two parties, one is typically a military and the other is typically a radicalist group. Radicalists groups typically will be using mock-soviet weaponry, commonly a Chinese Type 56. If one of the "soldiers" from the military group charges the radicalists with a sword, he will rapidly be in a fairly innacurate but still likely effective hail of 7.62x39mm rounds. He has to run 500m, which in typically military gear would be difficult, and would take about 1 minute. The radicalists have 1 minute to shoot him. They will likely hit him multiple times, causing broken bones, internal bleeding, if hit in unprotected areas, bullet wounds and likely death within that minute.
It wouldn't be effective at all. That's why we stopped using swords commonly as soon as we discovered effective guns.