The struggle between Capet and Plantagenet was originally one between French nobles : the king and the duke of Guyenne, who happens to be King of England to. Even at the beginning of the hundred years war, when the Plantagenet claimed the French throne this wasn't but an excuse to stess their claims in Guyenne and elsewhere in western France.
At the end of 14th century this would change. In 1392 Charles VI of France becomes crazy. He will float the rest of his life between daft and complete insane. Since then the domestic politics of France are dominated by the question of who will dominate the regency : the king's uncle the Duke of Burgundy and his Bourguignons party or the kings brother Louis I of Orléans and his Armagnac party. In England, in 1399 Richard II Platagenet is deposed and replaced by Henry IV of the house (Platagenet -) Lancaster. Richard's regime was based on oppression and heavy taxes and was not really popular. When he he pursued peace with France and desinherrited his cousin Henri Bollinbroke, the basket of the barons was full. Henry IV was too busy to crush opposition against his government to bother about the war in France. When his son Henry V came to the throne in 1413 this would change. He would be the first English king since the Norman conquest to use English as government language. The conflict between Plantagenet and Capet changed so into a conflict between England and France. In 1415 Henry landed with a small army in Normandy. When after the conquest of Harfleur he marched to Calais, he and his weary troops were intercepted by a much larger French-Armagnac army at Agincourt. Not the French however but the British would leave the battlefield as victors. In 1417 Lower Normandy was concered and in 1419 Rouen fell and he English amy stood at the walls of Paris. On September 14, 1419 Jean sans Peur, Duke of Burgundy was murdered by supporters of the Duke of Orleans (whose father was murdered on Jean' sans Peur orders). Immediately Jean' heir Philips le Bon closed an alliance with England to avenge his father.
Although the Montford owed their duchy to the English and were financially dependent on them since Jean IV was heavily in debt, they succeded to remain neutral in the beginning of the conflict. However, they were slowly sucked in, in the renewed war and in 1419 were in open war with France and its allies. The Britton position was very uncomfortable. They were at war with the French king but they were not part of the English alliance. Moreover, the relations between England and Brittany were -100 as a result of the efforts of the Montfort to remain neutral and there was little chance to join the alliance before four other countries would belongs to it. With Brittany out of the English alliance, it would be eaten by England if England won the war. If England however would lose, it would be a victorious France who would swallow Brittany. The duchy was not really poor but the three provinces were compared with London, Paris, Lyon of Flanders no grease-pots. The treasury was full with 300 Ducats but the income was low, so the money had to be spend thriffty.
1419 would become an important year. Jean VI decided to actively participate in the war. Remaining at the side so that England's possessions would increases in size without Brittany itself strengthened was a disastrous scenario. Remaining at the side so England got the worst of it was a nightmare. The next victim of France would be Brittany itself! As Brittany had only 9000 men infantry and 1000 cavalry men,its contribution would be one of pillaging and looting behind enemy lines and a siege left or right without participation of real battles, hoping to get the war score high enough to get to get a war compensation. The first aim of a siege was Maine or the Vendee.
On the first of januari, the quality of the troops was improved and 2000 additional cavalry was recruited. In February, the Breton Regiment left Morbihan with 9000 men infantry and laid siege for Angers. This siege was immediately stolen by the Duke of Gloucester with a mere thousant cavalary men. In March the Breton regiment left for the Vendée. Because this was a English passage route between the north and Gascony and Vendée couldn't support much men this siege was not maintained and the regiment withdrew to English Poitou. The aim was to besiege the possessions of the Bourbons. The Bourbons however manned Berry with a strong army and finally in may siege was laid on Guyenne. The Brittons were quietly left alone by the other warring parties and, ultimately, the city handed itself over on July 20, 1420. On September 19 Brittany regiment reached the walls of Limoges and laid directly at the siege. The Bourbon armies in meantime had taken part in the sieges of Dijon and Besançon and was now bound to the siege of English Orleans. So the the siege of Limoges went its way quietly, on exception of a skirmish with fresh recrute. On May 19, 1421 Limoges would fall. Preying and living of the country the regiment made its way thru Auvergne, Berry, Burgundy, Nivernais and Orleans to Ile-de-France, where together with the armée de Bretagne it started the siege of Paris on December 23. The Armée de Bretagne departed on April 1419 with 3,000 man cavalry on a marauding trip through southern France and Aragon*, trying to loot as much as possible and destroying small groups of fresh recrutes. In April 1421 the Army moves to the north in order to wrench as much as possible the economy. Finally the Armée would unite with the regiment at the siege of Paris.
To improve the position of the duchy an important sum was given to England on newyears day 1419. On January 2 Gelderland joined the English alliance, followed by Navarra on January 5! The fear that Brittany would remain out of the alliance was sparked by this. Fortunately, on April 1 in England accepted Bretange in the alliance. This would have immediate consequences. May 16, 1419 Aragon declared war on Navarra and Brittany was obliged to participate in this war. Except some pillaging by the Armée Breton, Brittany was not involved in this war and on April 9 England paid for the alliance peace for the ephemeral sum of 28 Ducat. Because Gelderland had not participated in the war its place in the alliance would be taken over by Granada. Pagan Muslims were now in "la douce France" to slaughter good French Catholics, something that until now was reserved to good English, Burgundians, Brittons and Bask Catholics. An improvement for the victims! Never trust perfid Albion! moreover, Portugal declared war on Granade on February 20. England supported Granada and the alliance had to follow. Brittany continued to pursue better relations with England and after an initial failed attempt a niece of Jean VI married with a son of the duke of Bedford, then regent of England.
In France the main participants in the conflict became exhausted. While France and its allies in 1419 were fielding much larger armies than the English alliance, only Scotland succeeded gaining ground.
Again and again the French armies were defeated by smaller but better-led English armies. The Breton systematically refused to take part in battles and the Burgundians withdrew back to the Netherlands where they recruited a new army and pushed the French out of Artois. Navarre, Gelderland and later Granada sent fairly large armies that did not laid down sieges, lost and won about the same number of battles and in general contributed to the deterioration of the French troops. On November 4, 1419 England annexed Orleans. On June 5, 1421 Auvergne closed a honorable peace with the English Coalition and the status quo was restored. After the fall of Berry to the English and Limoges to Brittany, Bourbon capitulated in November 1, 1421. The Limousin was ceded to Brittany 32 ducats were paid to the alliance and Bourbon gave military access to England.
Remark the regiment marching to Nivernais and the armée looting Picardie
On September 2, 1422 Henry V died, leaving the throne to his newborn son Henry VI. Two days later France and the remaining allies the Provence, Scotland and Lotheringen ceased the fighting. France agreed to pay 144 Ducat and hand over Vendée to England and Guyenne to Brittany.
While the war raged thru France, Brittany remained largely spared of the scourge. Only once a French Army wandered trough Armor and Morbihan. In the meantime, the ducal diplomacy was running at full speed. To improve Brittanies relations in the Mediterranean basin, marriages were sealed with Byzance, Castile and Cyprus. In the wake of this, Britton traders could exchange their cards with those of Cyprus and after some generously distributed money to Byzantine officials in exile in Tuscany, with the Byzantines. Thanks to Castilian cards Breton traders came to know more about North Africa and the Middle Atlantic ocean. In 1423, a group of whalers from St Malo and Dinard put hands on the maps of Norwegian masters and obtained their knowledge of Greenland and the waters around Terre-Neuve.
In 1419 war broke out across Europe as pimples on the face of a teenager. Byzance declared war on Athens, supported by Toscany. Gradually Modena, Siena and the Papal States would take part to the war. The Ottoman empire in turn declared war on Byzance. When Tuscany was annexed by Byzance, the Papal States made peace for 123 Ducat. While the war between Portugal Fez and Algiers ended with a compensation of 32 Ducat to Portugal, Granada, Fez and Algiers were attacked by Castile. When in addition to that Fez was attacked by Morocco, it was abandoned by its allies. In Northern Europe Sweden followed by Denmark declared war on Novgorod. When Sweden makes peace with Novgorod for Kola it prompt attacked Norway. Denmark does not follow Sweden but after closing a new alliance with Sweden, that country is again at war with Novgorod. The Scandinavians are not the only one after Novgorods skin: Pskov and Suzdal do too. Suzdal is bought of with 11 Ducat and the colony of Archangelsk and the annexation off Pskov by Tver effectivelly put an end to that conflict. Further Holstein, Meclenburg, Prussia, Pomerania and the Teutons are playing their classic robber bridge with Poland and Lithuvania. Brandenburg is seizing the opportunity to attack Pomerania, followed by Magdeburg and Saxony. Pomerania is supported by Meclenburg but Holstein, Prussia and the Teutons drops their allies. Eventually Meclenburg gets annexed by Brandenburg and Pomerania incorporates Magdeburg. In central Europe, Mainz and Strassburg are annexed by the Pfalz but their aggressive behavior brings them into war with Hesse, Bremen and Hannover and Kleve, Cologne and Bavaria.
* The armee de Bretagne crossed following provinces: Vendée, Limousin, Auvergne, Cevennes, Languedoc, Roussillon, Lyonais, Dauphine, Provence, Languedoc, Roussillon, Gerona, Roussillon, Limousin, Poitou, Limousin, Guyenne, Berri, Poitou, Guyenne, Languedoc , Cevennes, Limousin, Berry, Burgundy, Orleanais, Ile de France, Picardie, Champagne, Artois, Picardie, Ile de France.
your outline is very historical and detailed, which I certainly admire (I am a history student after all) 
