As part of the Hundred Years War, England supported Flemish rebels in Ghent against the Count Louis "the Bad" and his son-in-Law Philip of Burgundy. Thanks to John of Gaunt's diversion of resources to Spain (whose throne he had a claim to) and general malaise and political incompetence in England, the English did not land an army in Flanders until 1382, after Louis, with French assistance, crushed the Flemings at the battle of Roosebeke.
So let's say, for whatever reason (John of Gaunt falling off a horse etc.), the English settle on intervening in the Flemish Revolt sooner. The addition of 6000+ English soldiers probably is enough to prevent the Flemish defeat at Roosebeke, though it almost certainly triggers a French intervention (Charles invaded with something like 30,000 soldiers, though the French were forced to withdraw fairly quickly due to lack of funds). Alternately, if we go back to the 1350s, perhaps Louis de Male marries Margaret to Edmund of Langley.
It seems to me that if England can secure control over Flanders, then their position in Calais (and for that matter Artois) becomes much firmer, and they may or may not have a stronger basis for supporting their claim to France. Alternately, perhaps a peace deal at Leulinghem etc. trades renunciation of English claims in France for renunciation of French sovereignty over Flanders.
So let's say, for whatever reason (John of Gaunt falling off a horse etc.), the English settle on intervening in the Flemish Revolt sooner. The addition of 6000+ English soldiers probably is enough to prevent the Flemish defeat at Roosebeke, though it almost certainly triggers a French intervention (Charles invaded with something like 30,000 soldiers, though the French were forced to withdraw fairly quickly due to lack of funds). Alternately, if we go back to the 1350s, perhaps Louis de Male marries Margaret to Edmund of Langley.
It seems to me that if England can secure control over Flanders, then their position in Calais (and for that matter Artois) becomes much firmer, and they may or may not have a stronger basis for supporting their claim to France. Alternately, perhaps a peace deal at Leulinghem etc. trades renunciation of English claims in France for renunciation of French sovereignty over Flanders.