Bilateral trade shocks affect firms in third countries by redirecting demand and reallocating competition across markets, creating winners and losers. We propose a tractable trade model with heterogeneous firms to decompose firm-level export responses as a function of destination-specific changes in demand, own-price and cross-price elasticities, and external economies of scale. Using the 2018?2019 US-China trade war as a source of exogenous variation and data on the universe of Italian firms, we show how bilateral trade shocks occurring elsewhere identify these primitives for third countries. On average, the US-China trade war created a 2.5% export gain, albeit with substantial heterogeneity across firms. The external economies of scale channel accounts for three-quarters of changes in export performance.