Entity.Save is what I need.

No concern about whether field values have changed or if the entity is in sync. I want to save the entity to persistent storage. The entity I want to save has not changed, but the persistent storage may have, the entity is the correct state to be saved and in essence it needs to update persistent storage to have the correct state.

How can this be accomplished?

Thank you!

More correctly said, how can an entity that hasn't been changed be saved?

Adapter.SaveEntity(entity) is the call, but if the entity hasn't had a value change, how can this be forced?

Looks like I found the answer.

The process uses the entity.SaveFields and RollbackFields methods to capture and rollback the state.

foreach(entity ent in _entities)
{
    ent.RollbackFields("original");
    foreach(IEntityField2 field in ent.Fields)
    {
        if (field.IsReadOnly == false)
        {
            ent.Fields[field.Name].ForcedCurrentValueWrite(ent.Fields[field.Name].CurrentValue);
            ent.Fields[field.Name].IsChanged = true;
        }
    }
    ent.IsDirty = true;
}
_adapter.SaveEntityCollection(_entities);

As a matter of fact, this line isn't necessary:

ent.Fields[field.Name].ForcedCurrentValueWrite(ent.Fields[field.Name].CurrentValue);

Thank you, daelmo, that worked.