Domestic political clashes over trade are as old as commerce among nations, but the character of these struggles has varied across history. They can sometimes arise over shifting coalitions of business and labor groups positioned on both sides (e.g., the 1932 Smoot-Hawley Act). Other conflicts have emerged between larger classes or sectors, such as the British free trade movement in the nineteenth century that pitted workers and capitalists against the landed elites. In this elegant and innovative work, Hiscox explains the variations in trade cleavages and conflicts. He argues that the mobility of factors decisively shapes the battle lines of trade. When factors are mobile (e.g., labor and capital), trade's income effects fall along class lines; when factors are immobile (e.g., land), these effects are more likely to follow industry lines. Among his implications: although class conflict can be disruptive to society, it can also create more encompassing political coalitions that push for economic policies that are efficient for the society as a whole. Furthermore, societies should provide extensive forms of adjustment assistance and other compensation to make workers' assets more mobile, thereby undercutting the rent-seeking of industry-oriented trade politics.