The first two chapters of the book basically set up everything that will unfold, as an initial situation should. We learn of Robert Jordan's military mission, and become acquainted with the spot where it will take place. We meet the people he'll have to work with, and whom he has to win over, particularly Pablo, who we learn from the first may be a problem. And we meet Maria, who right from the get-go makes him "thick-in the throat."
Although we haven't been getting good signals from Pablo since Robert Jordan met him, it's at this point that it becomes clear he'll be a serious problem to the mission. Agustín's warning confirms Anselmo in his own suspicion that Pablo is not trustworthy, which confirms Robert Jordan's. And no sooner do they return than Pablo opposes Robert Jordan. Although Pilar wins everyone else over to his side and gives Pablo the proverbial boot from his post as ruler of the roost, Robert Jordan's made an enemy. Furthermore, Pablo himself isn't the only problem; Pablo's resistance is motivated by his perception of how bad the mission might be. From this point on, things look less promising.
Things get steadily worse. An unusual May snowstorm strikes up. While it's brewin' outside, a potentially lethal confrontation with Pablo ensues. It doesn't lead to anything except irritation (and a deeper doubt about Pablo), but when the snowstorm stops, El Sordo's doom is guaranteed. The next day, El Sordo and his band are lost to fascist bombers. Progressively more characters also realize during this time that their chances of surviving the attack are less likely than they thought. And it appears the fascists know about the Republican offensive. The one compensation in all of this for Robert Jordan: Maria. That raises new problems too, though: the stakes of risking his life are now much higher. Direst moment: Pablo steals the detonators.
Just when all seems lost…he's ba-ack! The return of Pablo with five men and a newfound courage and camaraderie is the turning point of the book. From this point, chances are the mission will be successful.
After the climax, it's still unclear whether or not the larger Republican attack will be successful, but things look grim. Our hopes are with Andrés as he struggles to reach Golz, but it quickly becomes clear the attack can't be called off when bombs start falling. Meanwhile, the bridge operation does go through, but with losses. It's also clear soon enough that the larger attack has failed. The last burst of suspense comes as the surviving guerillas try to make their escape. One by one they do, until it's just Robert Jordan…and he gets shot in the leg.
At this point, it's largely decided how things will end, and we're just waiting for the book to wind down. Maria and Robert Jordan have a hard good-bye, but the others are able to take her away. He's left to die, which gives him one last opportunity to reflect on all of the experiences the book has recounted. It looks for a moment as if he might kill himself.
Robert Jordan, as at peace with death as he'll ever be, overcomes the temptation to kill himself and stays alive and conscious long enough for an opportunity to die in a blaze of glory to present itself. We leave him lying in wait on the forest floor, where the book began. We don't see what happens, but it's all over folks.