sentences:  Influenced by Chamberlain, Salisbury sanctioned Sir Edmund Monson, British Ambassador in Paris, to be more assertive in negotiations.The subsequent concessions made by the French encouraged Chamberlain, who arranged for a military force, commanded by Frederick Lugard, to occupy areas claimed by Britain, thereby undermining French claims in the region.In a risky 'chequerboard' strategy, Lugard's forces occupied territories claimed by the French to counterbalance the establishment of French garrisons in British territory.