Enraged by this "rebellion", Juan I ordered a host of 31,000 men to engage in a two-pronged invasion in May. The smaller Northern force sacked and burnt towns along the border, before being defeated by local Portuguese nobles in the battle of Trancoso, in the first week of June. On the news of the invasion by the Castilians, John I of Portugal's army met with Nuno Álvares Pereira, the Constable of Portugal, in the town of Tomar. There they decided to face the Castilians before they could get close to Lisbon and lay siege to it again.