We present a unified explanation of the internationalization strategies of major mobile network operators (MNOs). We have developed a framework that analyzes the strategies of major international MNOs in terms of the relationship between their degree of involvement in international business operations and the degree of equity participation. The results show a positive association between these two dimensions as expected, but they also reveal some exceptional cases in which certain MNOs are actively involved in the business operations of other foreign MNOs, even with minor (or zero) equity investments. In this paper, we argue that the strategic actions of the major MNOs which are the largest shareholders of foreign MNOs are in an equilibrium status because these major MNOs derive maximum benefit from full or considerable management control and active involvement. Finally, we predict that latecomers (MNOs who are just about to enter foreign telecommunications markets) may adopt an incremental investment approach because most developed markets and deregulated emerging markets with growth potential are already preempted by major MNOs. Therefore, the window of opportunity for internationalization in those markets is currently small.