There is a total of 46 Intel collectables throughout the campaign. Some will be in plain sight, while others may be a little trickier to spot. Don't worry if you miss one while you play, as you can return to any of the previous levels via level select. If any Intel are missed, replay through it on Easy to make death a little less constant while searching. Depending on your playstyle, sometimes it may be better to head back through on Easy from the start.