Why did the Union fall back on the Anaconda Plan?

the two sets of lines are :

and remember beauty,five-wits,strength,and discretion ,they all at the last do everyman forsake (to leave forever ) for after death amends may no man make,for then mercy and pity doth him forsake.(to leave forever )

Texas’ gulf coastal plains are the western extension of the coastal plain extending from the atlantic ocean to beyond the rio grande. its characteristic rolling to hilly surface covered with a heavy growth of pine and hardwoods extends into east texas. in the increasingly arid west, however, its forests become secondary in nature, consisting largely of post oaks and, farther west, prairies and brushlands.