# When Ephraim saw his sickness, and Judah saw his wound

Both Ephraim (the northern kingdom of Israel) and Judah (the southern kingdom of Israel) realized that they were in danger.

# then Ephraim went to Assyria, and Judah sent messengers to the great king

Ephraim and Judah asked Assyria for help instead of asking Yahweh for help. "Great king" was a title for the king of Assyria.

# But he was not able

Here "he" refers to the king of Assyria.