on 17 june, 29th infantry division was among the first german units to reach the border to switzerland, meaning that any remaining allied soldiers on the maginot line were now threatened to get completely cut off. the panzer group now turned its attention towards the trapped french troops, and xxxix army corps was turned north-east towards belfort and the upper moselle river. the goal of these operations was to connect with 7th army under friedrich dollmann. as panzer group guderian now operated in very tight conjunction with von leeb's army group c, it was transferred from its previous army group to von leeb's command. von leeb instructed panzer group guderian to advance towards belfort and épinal, which was the same general idea that guderian himself had ordered.