PARIS — European nations moved on Wednesday to intensify their involvement in Iraq, announcing further humanitarian aid and, for the first time, pledging to supply arms to the embattled Kurdish forces fighting the Sunni militants who have overrun much of northern Iraq.

The shift is an important one for Europe, where the legacy of the first Iraq war remains divisive, but several factors in the current conflict are steadily tilting nations here toward deeper engagement now that President Obama has begun sending military advisers for the first time since American troops left in 2011.

Analysts said that the images of dusty families sleeping in the open on a barren, rocky mountain had put pressure on officials to take action, despite what for many here remains the toxic legacy of the American-led invasion of 2003.

For Europeans, the specter of a humanitarian calamity — particularly involving what is being portrayed here as a Christian minority — has resonated.