Why did Wilson think the Rebels had killed half his regiment?

So many men were missing or disjointed from the group after that battle that he'd thought they'd almost all been kiiled; it turned out to be about half.

"Th' reg'ment lost over half th' men yestirday," remarked the friend eventually. "I thought 'a course they was all dead, but, laws, they kep' a-comin' back last night until it seems, after all, we didn't lose but a few. They'd been scattered all over, wanderin' around in th' woods, fightin' with other reg'ments, an' everything. Jest like you done."