Generations of soldiers have guarded the country's frontier.
Tips
memory
Picture the right side as fields (田) stacked with dividing lines between them: that is exactly a 疆, the boundary line marking off territory. Common in 边疆 (frontier) and 疆域 (territory).
The right side is two fields 田 with lines drawn between and around them. It both gives the sound jiāng and pictures the dividing borders themselves, the heart of this character's meaning.
Filed under radical 田 (tián, #102) by convention. 田 is not a separate component in 疆, so no strokes are highlighted.