I am happy to help you with your outline and the comparison between the two books. You don’t mention the exact thesis here, so allow me to suggest one. How about this: Both A Farewell to Arms and The Bridge on the Drina focuses on the importance of connection due to two “characters”: Catherine and the bridge. The first section of your outline, then, should lead into this particular thesis statement.
The second part of your outline would be the first body paragraph. Begin with a topic sentence like, “The two books need a connection because of the tragedy of war.” In A Farewell to Arms, the war is World War I, and Frederic Henry describes it in detail. Specifics can be included, such as the battle in which the character is wounded, so that you can include examples. In The Bridge on the Drina everyone needs a connection because of many wars from the 1500sto the 1900s. Here some specifics can be given about the suffering of the Bosnian people.
The next part of your outline would be the middle body paragraph. This one should focus as Catherine and “the bridge” as characters that serve to unify. It is a love connection with Catherine that helps Frederick Henry along through the destruction of war. An example can be him getting lost “in her hair” as well as their travels and conversations. A further example could be the child they conceived together. In The Bridge on the Drina the connection the bridge from the title built across the Drina River near Viegrad. It serves as the connection between the Bosnian people and the Turks. After it is accepted (which takes a while), the connection is significant.
Next, your outline should have a final body paragraph. Again, begin with a topic sentence which would include the end of the connection. In A Farewell to Arms, the end of the connection is the baby’s death and then Catharine’s death. This destroys all hope for Frederick Henry. In The Bridge on the Drina the end of the connection is the “death” of the actual bridge. It is destroyed in the same war as Catherine is destroyed: World War I.
The final part of your outline should be about your conclusion. Reword your thesis statement here and suggest a new idea of unity or connection in the world that is either being continued or lost. Perhaps the success of the NATO or the United Nations could be an example.