History crossword

2. Man who assassinated Franz Ferdinand in 1914.
6. The deadly area between opposing trenches.
10. Payments Germany had to make after WWI, as punishment.
12. Country Germany invaded, causing Britain to enter WWI.
13. One of the four MAIN causes of WWI; agreements between nations to support one another.
14. A pilot who shot down at least five enemy planes.
15. Disease caused by standing in wet trenches for too long.
18. One of the longest and bloodiest battles of WWI, fought in France.
19. First Canadian to command Canadian troops in WWI.
20. City where Archduke Franz Ferdinand was assassinated.

1. Forced military service, introduced in Canada in 1917.
3. German submarine used to sink Allied ships.
4. Canadian flying ace who was one of the most successful WWI pilots.
5. German Kaiser who supported Austria-Hungary in 1914.
7. Psychological trauma suffered by many WWI soldiers.
8. Type of WWI aircraft with two wings stacked on top of each other.
9. Famous German flying ace, also known as the Red Baron.
11. French leader at the Treaty of Versailles who wanted to punish Germany.
16. Where soldiers lived and fought in WWI; muddy, unsanitary, and dangerous.
17. British ship sunk by a German U-boat, pushing the U.S. closer to war.