[@FalloutJack]
[@LetMeDoStuff]

VC 1 Design Archive - the big one, lots of dev notes and lore. VC1 is set in the Gallian theater of the Second Europan War (EW2). It includes the most info about the First Europan War (EW1), too.
http://www.mediafire.com/file/5ciw3mcp0thrp9q/Valkyria_Chronicles_1_Design_archive_%255Benglish%255D.zip/file

VC 1 Artbook - mostly duplicate stuff from the VC1 Design Archive, but get it if you're curious.
http://www.mediafire.com/file/4pq7jbei8mh1hwi/Valkyria_Chronicles_-_Artbook.zip/file

VC 2: World Artworks - VC2 is set after the end of the Gallian theater of EW2, but before the war in Europa ends. 
http://www.mediafire.com/file/jbbnbkrctf3qzwa/Valkyria_Chronicles_2_artbook.zip/file

VC 3: Complete Artworks - VC3 takes place at the same time as VC1. 
http://www.mediafire.com/file/81aqrayhji8c2y7/Valkyria_Chronicles_3_complete_artworks.zip/file


[@FalloutJack][@caliban22][@Sola][@Conscripts]
This game aside, in the VC world tanks are definitely a thing in EW1. The East Europan Imperial Alliance fielded them first, but Gallia also had a tank corps by the time of EW1. Belgen Gunther, the father of Welkin Gunther of VC1, was first noticed for his abilities as a tank commander during the Imperial invasion of Gallia in EW1. The Edelweiss, developed with cutting edge technology by Belgen Gunther and Theimer shortly after EW1, is comparable to late-WWII tanks. The VC world picks up tanks faster than the real world does, in part because of the existence of ragnite. Ragnite, processed into ragnoline, allowed for smaller, more powerful, more efficient engines than the real world had at the "same" time. 

It's a good rule of thumb to assume that land military tech, at least, for any given year in the VC world is a few years ahead of where it would be in the real world. One example of that is that everyone is using semi-automatic rifles as their main service arm by the time EW2 starts (1935), down to the town guard of a small corner of Gallia called Bruhl.

EDIT: Another hint to the widespread use of tanks in EW1 is that everyone, by the time EW2 rolls around, has lots of Lancers -- that is, troops using infantry-portable anti-tank weapons. This suggests a reaction to EW1 tank tactics, that the average infantry formation was expected to encounter enemy tanks. EW2 armor doctrine also hints to it's widespread use, as tanks are assigned to formations as small as infantry platoons as organic armor assets.