Final answer:
Houyhnhnm Yahoos struggle with cooperation during large-scale conflicts due to the challenges of maintaining discipline and order in a large army.
Step-by-step explanation:
When the Houyhnhnm Yahoos are engaged in large-scale conflicts, they are usually unable to achieve cooperation. This difficulty in uniting large groups for a common cause is tied to the inherent challenges in maintaining order and discipline within vast armies.
Strategies such as forcing marches to gain an advantage (making forced marches covering double the usual distance), or taking defensive stances to avoid confrontation (prevent the enemy from engaging us), are mentioned as tactics in warfare.
Furthermore, the importance of coordination through signs and signals, and the consequences of insubordination are highlighted as factors that can lead to ruin (higher officers...give battle on their own account).