The defense of early frontier forts centered on the blockhouse, from which attackers could be put under a deadly barrage and to which defenders could retreat for a last-ditch fight if the stockade wall was breached. One blockhouse here is eight-sided and the opposite one is seven-sided. For the fort’s defense, the Russians brought in 41 cannons of various sizes and origins and established themselves so strongly that the meager Spanish forces to the south realized they could not evict them.