london britain tuesday welcome commitment u.s. president donald trump step military campaign taliban insurgents afghanistan president trump commit unite state open-ended conflict afghanistan monday night reverse course campaign pledge britain along european ally pledge troop support afghanistan military june u.s. secretary defense jam mattis say time troop number country reduce rapidly u.s. commitment welcome british defence secretary michael fallon say statement call secretary mattis yesterday agree despite challenge stay course afghanistan help build fragile democracy reduce terrorist threat west interest afghanistan become prosperous safe ‎announced troop increase back june britain welcome trump 's renew commitment afghanistan