So. When the guy on a history board who randomly keeps the name of a SS division says "obsolete", he means "as effective as any other torpedo bomber".
Considering that we're talking about how land based fighter planes would do against more modern land based fighter planes, your non sequitur point and personal attacks add nothing to the conversation and really are just trolling derailments because of what I can only assume is a personal grudge.
Well, first of all I can see it wasn't even breached, but surrounded: the border with Yugoslavia wasn't well defended (even by the standards of anything that wasn't the frontline in Albania), the Germans drove down to Thessaloniki, isolated most of the line, and forced a surrender. Attempts to break through the line before that failed, despite the extremely meager garrison of sixty thousand or so reservists and green recruits. This is what you're comparing the weakest part of the Italian defenses to: something that stopped dead the German attack while being manned by the scraped bottom of the barrel.
So mountain troops flanked a fortress line, isolated 60,000 men and forced them to surrender. Sounds like a model of how things would operate along the less fortified Italian-Yugoslav border. Especially considering the Italian defenses were the least built up in that area and weaker than the Metaxas Line. Why bash your head against a heavily defended point that won't fall easily without heavy losses when it was flank-able and able to be forced to surrender from behind?
That was the writing on the wall, but it did not stop nations from introducing biplanes up to the end of the Thirties or so. The Gladiator was brought in in 1937, the I-15 saw extensive use in all phases of the Spanish Civil War, and the Swordfish has reached memetic fame, to this point. There was a push to move to monoplanes, though, and Italy was not that far behind on that: the Macchi and Gabrielli series planes were already around by that time, the Reggiane Re.2000 were starting to come out, and so on.
And all were replaced ASAP by monoplanes, as they fell victim quickly to the faster more modern aircraft as soon as enemy pilots figured out tactics to fight them. In terms of the Soviet biplanes and monoplane version of them the I-16, see how they did during Barbarossa even after the Soviets realized they were at war.
The Italian monowing planes were coming, but were only introduced in 1940; in fact the Re.2000 was IOTL rejected by the Italian air force and only kept in production initially for foreign orders. 80% of total production went to foreign countries in the end. The Macchi C.200 only entered combat in June 1940 and in their debut lost one aircraft in combat with no kills in return.
Woefully unprepared, as far as equipment went; in far better shape when talking about doctrinal preparation and morale (for this specific purpose, I should add: if the Moose decides they can and should smack the Poseur and take Austria pronto, God help them).
Doctrinal preparation? I don't recall the Italian army being in particularly good shape there, especially in terms of training; after the debacles of 1940 they had to extensively retrain, which admittedly worked out very well despite being materially hampered throughout the war. Besides, didn't someone else already point out they were in the midst of a OOB reorganization when Mussolini declared war? And yes attacking Austria in 1939 through the Brenner Pass isn't going to go well for them, same as Germany trying to go the other way.
The valleys are killboxes, mostly. Passing through is going to exact extreme costs on the German army, and it's not like one go is going to be enough.
Based on? WW1 demonstrated otherwise repeatedly. Plus the Germans were able to flank the Metaxas Line via a valley without issue.
I just don't think Germany can floor France while keeping Italy in check. OTL was an extremely close and chancy thing already.
How many men do you think would be required to check Italy at the Brenner Pass? It was selected by Italy as the border because of how defensible it was, which applies from the other side as well. It probably could be held by 3rd line reservists as well. Again, on either side, so it's not like the Germans could successfully storm it either, hence all the talk about the Yugoslav side of things. And to be fair to the Italians in 1940 going through the French side isn't really a good option either.
It wasn't thougher, it wasn't well manned, and it still wasn't breached.
From what I've been able to find about the Italian border defenses, the Metaxas Line was stronger than what the Italians had built up against Yugoslavia or even Germany as of 1940, as the Italians had plowed nearly everything into the defenses against France until 1938. Well manned in relative, but given the mileage and number of men it was pretty well defended given that the entire point of the position was that it was easily held by troops not fit for a field army until the field army could show up if needed.
And to whether it was breached, you're right, frontally it wasn't, but it was flanked, so it fell anyway. Since the Italian defenses in the area we were talking where the invasion would come were even less well developed there was plenty of options to flank defenses. BTW since you brought up valleys as death traps it doesn't seem like it was for the German mountain corps that flank and defeated the Metaxas Line...
Also the Germans did breach the Aliakmon Line defended by the British:
https://en.wikipedia.org/wiki/Battle_of_Vevi_(1941)
https://en.wikipedia.org/wiki/Battle_of_Kleisoura_Pass
It just doesn't make sense for Italy to jump side wholesale at any point after 1938 or so, not when it has already helped Germany win several diplomatic battles. At most, it's going to sulk on the side. If it's solidly on the Allied side, then it's been so since the Stresa Front times, probably by taking Hoare-Laval, being gentler in Ethiopia, or even just containing its representatives to the LoN not to be absolute assholes.
Agreed. So much would have to change pre-1939 that if anything WW2 might well end up not being able to happen, at least as we know it, in this scenario. Plus if the Brits and French allow for Austria to be taken over per OTL then Italy might well end up defecting from the Allies anyway out of frustration.