A gerund phrase includes the gerund and its modifiers, so "Camping near a lake" would be the gerund phrase. Its noun use is as a complement to the subject, which is the "popular pastime for retirees".
If this was about Japan, they called for expansions into
other territories and launched military campaigns and the country became more
militaristic. They invaded China and seized Manchuria. This would lead to invasion and occupation of
other Asian countries as well.