Which sentence in this excerpt from Abraham Lincoln's Second Inaugural Address shows that he believed the Union was forced into war to ensure that the country remained united?

Hello. You forgot to put the passage to which this question refers. Here is the excerpt:

On the occasion corresponding to this four years ago, all thoughts were anxiously directed to an impending civil-war. All dreaded it—all sought to avert it. While the inaugural address was being delivered from this place, devoted altogether to saving the Union without war, insurgent agents were in the city seeking to destroy it without war — seeking to dissolve the Union, and divide effects, by negotiation. Both parties deprecated war; but one of them would make war rather than let the nation survive; and the other would accept war rather than let it perish. And the war came.

One eighth of the whole population were colored slaves, not distributed generally over the Union, but localized in the Southern part of it. These slaves constituted a peculiar and powerful interest. All knew that this interest was, somehow, the cause of the war. To strengthen, perpetuate, and extend this interest was the object for which the insurgents would rend the Union, even by war; while the government claimed no right to do more than to restrict the territorial enlargement of it. Neither party expected for the war, the magnitude, or the duration, which it has already attained. Neither anticipated that the cause of the conflict might cease with, or even before, the conflict itself should cease. Each looked for an easier triumph, and a result less fundamental and astounding. Both read the same Bible, and pray to the same God; and each invokes His aid against the other. It may seem strange that any men should dare to ask a just God's assistance in wringing their bread from the sweat of other men's faces; but let us judge not that we be not judged. The prayers of both could not be answered; that of neither has been answered fully.

"Both parties deprecated war; but one of them would make war rather than let the nation survive; and the other would accept war rather than let it perish."

Explanation:

With the phrase shown above, Lincoln shows how the entire nation feared war, but was divided with the concepts of sovereignty and power, making part of the country (the confederates) fear war, but were willing to start it, even that this would bring about the end of the nation. Because of this thought, the union (which did not want to wage war under any circumstances) was forced to join the fight and fight those who thought war was a solution. Only with the participation of the union would the country remain united and that was a sacrifice that the union had to make.

the years following the end of world war i were a period of deep social tensions, aggrevated by high wartime inflation. food prices more than doubled between 1915 and 1920; clothing costs more than tripled. a steel strike that began in chicago in 1919 became much more than a simple dispute between labor and management. the steel strike of 1919 became the focal point for profound social anxieties, especially fears of bolshevism.

organized labor had grown in strength during the course of the war. many unions won recognition and the 12-hour workday was abolished. an 8-hour days was instituted on war contract work and by 1919, half the country's workers had a 48-hour work week.

the war's end, however, was accompanied by labor turmoil, as labor demanded union recognition, shorter hours, and raises exceeding the inflation rate. over 4 million workers--one fifth of the nation's workforce--participated in strikes in 1919, including 365,000 steelworkers and 400,000 miners. the number of striking workers would not be matched until the depression year of 1937.

the year began with a general strike in seattle. police offers in boston went on strike, touching off several days of rioting and crime. but the most tumultuous strike took place in the steel industry. then some 350,000 steelworkers in 24 separate craft union went on strike as part of a drive by the american federation of labor to unionize the industry. from management's perspective, the steel strike represented the handiwork of radicals and professional labor agitators. the steel industry's leaders regarded the strike as a radical conspiracy to get the company to pay a 12-hour wage for eight hours' work. at a time when communists were seizing power in hungary and were staging a revolt in germany, and workers in italy were seizing factories, some industrialists feared that the steel strike was the first step toward overturning the industrial system.

the strike ended with the complete defeat of the unions. from labor's perspective, the corporations had triumphed through espionage, blacklists, and the denial of freedom of speech and assembly and through the complete unwillingness to recognize the right of collective bargaining with the workers' representatives.

during the 1920s, many of labor's gains during world war i and the progressive era were rolled back. membership in labor unions fell from 5 million to 3 million. the us supreme court outlawed picketing, overturned national child labor laws, and abolished minimum wage laws for women.