I suspect that many officers at the beginning of the war, regimental or field, would now be classed as 'peacetime officers', that is, not battle-proven. They would have some knowledge of tactics and the drills required, but would expect ALL the men to behave as they expected and no consideration given to standards or even physical differences. They would receive their baptism of fire at the same time as their unit. The regimental officers, principally company commanders, were expected to lead from the front and therefore many would be casualties in their first action.
As with many armies, the field officers would be either 'time-served' or 'well-connected' with little regard to ability and little practice at leading in the field. Any 'front line' experience would be long ago and not necessarily line of battle. Most would be more conversant with open country and battle lines.
This would begin to change after the first few battles and skirmishes. As the officer casualties increased - or their performance left something to be desired - they would be replaced, but not necessarily by anyone with experience. Sure, sergeants would get commissioned if they showed well in battle, but often the company sergeant WAS the company man, the guy who 'made' the company, not the officer. (There were few 'Sharpe's around) . Technology was new and the tactics still revolved around rifle drills and rank discipline. Exactly the same situation faced the British army in 1854 in the Crimea and the Austro-Hungarian Army in 1866, with different outcomes. Luck has a lot to do with it too!
This would also apply to the British Army 1939-42 and, to some extent, the US Army 1942-3.