Elisha the prophet acts as an intelligence source, protecting the Israelite king from secret enemy ambushes. Whenever danger arises, the prophet sends an urgent message instructing the king to avoid traveling along a specific route [רש״י, ביאור שטיינזלץ]. This caution is necessary because the Aramean king and his soldiers are waiting in those exact locations with the intent to capture the Israelite king [רלב״ג].
The commentators agree that the enemy forces were actively setting up camps to lay an ambush [רש״י, ביאור שטיינזלץ, רד״ק]. They offer two complementary explanations for how these troops concealed themselves. The primary approach among commentators suggests that the soldiers descended into topographically low areas, such as the bottom of a mountain, using the deep terrain to hide effectively [מצודת ציון, רד״ק, רלב״ג]. Another perspective adds that the soldiers remained entirely still and quiet, waiting in their positions without making a sound so that their presence would not be discovered [רלב״ג].
These warnings from the prophet occurred several times. The Israelite king made it a practice to investigate the locations he was warned about, and he always found the prophet's information to be perfectly accurate. Through these repeated failures, the Aramean king eventually realized that his most guarded military secrets and hidden ambush spots were completely exposed to Israel [רלב״ג].