11. Natural obstacles were used to advantage to channel attackers into coordinated fields of fire.12. There are no trees or natural obstacles near the track. 13. They were left with an extensive front, without natural obstacles which could favour the defense. 14. The last remaining natural obstacle separating the Union forces from Atlanta was the Chattahoochee River. 15. Cross country is the most exciting part with about 40 solid man-made and natural obstacles . 16. First, an attempt was made to clear the natural obstacles , but that proved too expensive. 17. In addition, the Soviet border was marked by a natural obstacle the Zbrucz river. 18. By June 16, there were no further natural obstacles in front of the American forces. 19. No natural obstacles remained between the Belgians and the German Army; retreat was not feasible. 20. Between there and the community of Kimball, the route veers several times to avoid natural obstacles .
